Prologue Magazine

Safeguarding Hoover Dam during World War II

Summer 2003, Vol. 35, No. 2

By Christine Pfaff


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Close-up of a section of Hoover Dam, 1942, by Ansel Adams.

As the Great Depression deepened in the early 1930s, a monumental civil engineering project known as the Boulder Canyon Project captured the nation's attention and stirred its imagination.

Coming amid widespread poverty and unemployment, the massive project not only provided jobs to thousands of unemployed men but offered some of the most complex engineering challenges ever tackled. Perhaps as important, it asserted America's ability to overcome extreme adversity with technical ingenuity, physical prowess, and unwavering resolve.

The project's goal: Build a huge dam—the largest ever built—across the Colorado River on the Nevada-Arizona border to harness the power and riches of the mighty river. Completed in 1936, Hoover Dam,* through the generation of electricity and the orderly dispersal of its waters, fueled the incredible growth of southern California—its large cities, its industrial base, its massive agricultural industry—and created Lake Mead, the world's largest man-made reservoir.

The construction saga and tremendous impact of Hoover Dam have been chronicled countless times over the past seventy years. Few people are aware, however, of the measures taken during World War II to maintain the dam's safety and very existence.

Tucked among the myriad official government documents housed in the National Archives and Records Administration are a series of plain brown files marked "confidential." They reveal the as-yet-untold and riveting story of the government's efforts during World War II to thwart potential sabotage of one of the nation's most strategic and vulnerable targets—Hoover Dam.

At stake was the electrical power it was providing to southern California, home of some of the nation's biggest defense plants, where planes and tanks and other armaments would be built on a round-the-clock basis once America's mighty industrial machine went to war.

The concrete in Hoover Dam had barely set when the first uneasy rumblings of a potential war in Europe were felt abroad, but it all seemed far removed from the remote Nevada desert where the world's highest dam had risen from the depths of Black Canyon to straddle the mighty Colorado River.

President Herbert C. Hoover, himself an engineer, approved funding for construction of the dam in 1930. The multipurpose structure would store irrigation water, provide flood control, and generate power to fuel the fast-paced growth of southern California. In designing and building the dam, U.S. Bureau of Reclamation engineers were tasked with some of the most difficult engineering challenges ever faced. When the last bucket of concrete was placed in the dam on May 29, 1935, the staggering 660-foot thick base almost equaled its height of 726 feet.

Security and law enforcement at the Boulder Dam Project evolved. Aside from the formidable technical and construction challenges, Reclamation was faced with handling safety, security, and law enforcement issues from the outset, since the project was located on lands ceded to the federal government by the state of Nevada. A small ranger force was created, consisting of nine Reclamation employees who were deputized as U.S. Marshals.

Early on, concerns centered on policing the Boulder City Reservation, home to the thousands of workers on the project. But after the dam opened, Reclamation's safety and security concerns shifted to the dam and powerhouse, where throngs of eager visitors were guided past gleaming turbines and generators. Reclamation, not in the business of catering to tourists, teamed up with the National Park Service, which took charge of developing the newly created Lake Mead for recreational purposes, leaving Reclamation in charge of tourist facilities at the dam and powerhouse.

Protecting Hoover Dam against human as well as natural-caused damage was soon to become a critical issue—and a contentious one at that.

As Hitler's violent aggression accelerated in Europe and the Japanese army marched against its neighbors across the Pacific, Reclamation, and even the public, became more sensitive to possible enemy threats to the dam. Many visitors expressed concern about sabotage and wondered what precautions were being taken to prevent it. By 1939, reverberations from the escalating war directly reached remote Hoover Dam.

The possible effects on the dam of an emergency situation in the United States were described in a letter dated August 30, 1939, from Reclamation's acting commissioner, Harry W. Bashore, to Solicitor of the Department of the Interior Nathan Margold.

"It might be necessary to close Boulder Power Plant to the public, and to arrange for special policing of other structures and plants to provide protection from possible saboteurs," Bashore wrote. "At the outset, however, probably an additional watchfulness on the part of our own personnel would be sufficient."

The advice was timely. In early October, a ranger observed a German man accompanied by a woman taking large numbers of photographs in the vicinity of the dam. The ranger overheard the man severely reprimanding the woman for spoiling some of the pictures and said that it would necessitate retaking them. The ranger watched for the couple's return without results.

Heightened tensions across the country prompted Secretary of the Interior Harold Ickes to contact the War Department regarding the advisability of releasing certain printed materials to the public. Secretary of War Harry H. Woodring told Ickes that detailed plans and specifications of large dam structures should be restricted and under no condition be furnished to foreign governments. He also recommended increased security precautions at the federal dams themselves.

The War Department believed that personnel working at the dams were the greatest danger and should be carefully scrutinized. Visitors were also potential threats and should not be allowed to carry suitcases, parcels, etc. into the dams.

In response to Woodring's letter, Ickes wrote that the distribution of detailed plans and specifications would be restricted as requested. Regarding the suggested investigation of all employees to ensure their reliability and loyalty, he said the department had no funds appropriated for such work. Lastly, Ickes reflected that it would be advisable to apply the army's regulations governing tours of its installations to all federal facilities.

Within a few weeks, another report of possible sabotage to Hoover Dam instantly raised security concerns to new levels. On the evening of November 30, 1939, the State Department received word from the U.S. embassy in Mexico of an alleged plot to bomb the intake towers at the dam. German agents discovered in Mexico City were planning the attack in order to paralyze the aviation manufacturing industry located in Los Angeles. This would be accomplished by cutting off power transmission over the dam's high-voltage lines. Two German agents living in Las Vegas, one of them an explosives expert, had reportedly made a dozen trips to the dam to investigate the feasibility of the plan. They intended to attach bombs to the intake towers from a boat, which they would rent under the pretense of a fishing excursion.

The State Department immediately contacted Reclamation Commissioner John Page and advised that all navigation on Lake Mead, particularly in the vicinity of the dam, be suspended without delay. Page was told to keep all information regarding the plot highly confidential so as not to reach the public or the press. Reclamation instantly banned all private boats from Black Canyon. Within a few days, the agency announced further restrictions upon employees of and visitors to the dam. Employees would not be allowed to enter the dam except when on duty without special permission and would not be allowed to take anyone else into the dam without specific authorization. To enhance security, Reclamation increased its ranger force by several men, and the National Park Service increased its patrol activities on Lake Mead.

The new restrictions led to all sorts of speculation and rumors among employees, the public, and of course, the press. On December 7, 1939, A. E. Cahlan, a columnist for the Las Vegas Evening Review, described some of the rumors circulating, including that of a large net stretched across the lake just above the dam to catch any explosives. The writer reported that Reclamation denied all suggestions of a plot to sabotage the dam and insisted that the extra precautions were merely a response to the uncertain times.

Cahlan also shared with his readers a conversation that he had had with Frank Crowe, general superintendent of Six Companies, Inc., the builders of Hoover Dam, when the dam was nearing completion. He had asked the construction supervisor about the possibility of an attack on the dam. Crowe replied: "It can't be done. It's too massive a structure, too well built. Aerial bombs might knock off a few chips of concrete but could not materially damage the structure. And besides, the air currents, and general terrain are such that planes could hardly get close enough to make a direct hit."

However, the threats were taken seriously by Reclamation. The day after he received news of the possible sabotage plot, Page consulted with the Federal Bureau of Investigation (FBI) in regard to the organization and adequacy of Reclamation's police force assigned to protecting the dam and powerhouse. On December 9, 1939, he requested that the FBI send staff to the dam to assess the security in place and make recommendations for improving it.

Other precautionary measures were instituted at the dam. Floodlights were installed to illuminate the channel above the intake towers. The rumored wire net was hung from a cable across the lake, making it impossible for boats to get within three hundred feet of the intake towers. All of this was done with the greatest care to minimize disturbance to the visitors.

Other suspicious activities at the dam in late December further pointed to possible espionage. One evening, a National Park Service patrol boat was fired on by a rifle from the steep canyon wall. The bullet ricocheted on the water and luckily missed its target. Another night, a car was spotted hastily driving away from the switchyard, which was clearly posted as a no-trespassing zone. These and several similar incidents heightened awareness and precautions even more.

In early January 1940, J. Edgar Hoover, director of the FBI, reported to Page on the results of its survey at Hoover Dam. The report addressed physical security deficiencies as well as an assessment of the employees. Among the latter, no subversive activity was noted, and their loyalty was deemed "favorable." The FBI study concluded with thirty-eight recommendations, including increased security patrols at the dam and its vicinity; securely locking off specific areas of the dam; regular inspections for foreign materials that may have been deposited in key locations; and closer scrutiny of individuals, tour groups, packages, and vehicles entering and leaving the dam. The FBI also suggested that heavy metal gates be installed to create manned inspection stations in the roadways leading to the dam from Boulder City on the Nevada side and from Kingman on the Arizona side. Lastly, the FBI proposed that it be invited to conduct a security training school for the rangers and other appropriate personnel. Some of the recommended actions had already been implemented; others were considered good ideas by Reclamation; and a few were questioned as to their practicability.

Rumors of sabotage continued to fly in the media, prompting an official press release from John Page on January 9, 1940, in which he stated, "Boulder Dam is perfectly safe. There has been no 'plot' unearthed. Reports that the Bureau of Reclamation is fearful that someone will dynamite the dam are ridiculous. All rumors and reports that visitors are no longer welcome at Boulder Dam are entirely erroneous."

Although Reclamation continued to deny to the outside world any concerns about the safety of the dam, within the government it was an entirely different matter. On January 15, 1940, a resolution was submitted to the House of Representatives (H. Res. 356) directing the secretary of state to respond to numerous specific questions regarding the "conspiracy" to bomb Hoover Dam. The resolution was referred to the House Committee on Foreign Affairs, which recommended against passage due to security concerns. Instead, the Department of State furnished the House with information that was "consistent with the public interest."

In February 1940, the possible plot to sabotage Hoover Dam resurfaced with more frightening news. The War Department forwarded strictly confidential information to Reclamation that "Life and death orders have been given by Berlin to put L.A. in the black. Two large steam electric stations, one at Long Beach and one at some point below there, are going to be blasted. Last week German sabotage experts departed from Habana, Cuba, going through Miami. They are now residing in Long Beach. Unless quick action is taken, some terminal transformer station somewhere near Boulder Dam and another station in Los Angeles are doomed also to be sabotaged."

Discussions intensified within Reclamation to increase security measures at the dam, powerhouse, and Nevada switchyards. Additional gates, barriers, and doors were ordered at various strategic locations, and a scheme was developed to install heavy wire fencing on the surrounding cliffs. In mid-June, the FBI conducted its security training at Hoover Dam for 149 men. The lead trainer, M. E. Gurnea, conjectured that attempts to damage Hoover Dam would occur by stealth and not by force, except in a getaway in the event of discovery. Protective measures should be implemented based on that premise. Gurnea cautioned that the situation would change should the United States enter into the war, at which point additional security in the form of a military guard would be advisable. Gurnea suggested increasing the numbers of rangers patrolling the dam, powerhouse, and switchyard.

Despite all the precautionary measures instituted by Reclamation, the Department of the Interior was apprehensive that the potential dangers were beyond its ability to handle. On June 19, 1940, acting Interior Secretary E. K. Burlew wrote to the secretary of war asking that the military furnish armed guards to patrol and protect the project features. The response received from newly appointed Secretary of War Henry L. Stimson was not favorable. On July 18, he wrote: "In the event of a threat of sabotage on a scale that could not be met by the local guards, the Commanding General, 9th Corps Area, has authority to act without reference to the War Department. But no such threat is known to exist now. It would be uneconomical and unsound to dissipate our military strength using troops, which should be training for combat, to perform duties which can be performed efficiently by civilian guards and watchmen."

Reclamation then inquired if the War Department would at least be willing to substantially increase the small arms and ammunition for the rangers assigned to guard against sabotage. This request was also denied on the basis that all stocks of government arms and ammunition would be needed to meet the needs of the army. However, the Interior Department obtained clearance to purchase the equipment commercially. Congress also recognized the gravity of the situation, and on May 29, 1940, Senator Patrick McCarran of Nevada introduced a bill (S. 4066) to establish a fortified military post on federal land at or near Boulder Dam to provide adequate protection for the structure against injury or destruction.

Subsequent purported sabotage incidents in early July 1940 provoked further anxiety of a possible attack on Hoover and the need for increased vigilance. A Reclamation warehouse at Parker Dam was burned down, and in the ruins, fragments of an "infernal machine" were discovered. At the World's Fair grounds in New York an "infernal machine" hidden in a suitcase exploded, killing two detectives.

That summer, two fascinating proposals for protecting the strategic dam were submitted to Reclamation. No longer focused just on small sabotage attempts, both plans addressed direct bomb attacks, reflecting heightened fears. The first came from J. P. Durbin, a concerned resident of California, who had visited the dam frequently during construction and thereafter. Durbin suggested construction of a steel and concrete canopy arched over the narrow canyon to cover the dam facility. Rock and gravel added to the canopy would provide further resistance to damage from bomb attacks.

The second proposal was voluntarily submitted to the secretary of the interior by Oskar J.W. Hansen, the Norwegian-born sculptor who had recently completed the now famous pair of huge bronze winged figures at the dam. Hansen conjectured that Hoover Dam would be an easy aerial target for a determined enemy to find and destroy. He further speculated that Hoover Dam would be a first objective and would be prone to attack prior to a declared state of hostilities.

He proposed anchoring steel cables into the canyon walls to form a protective grid over the vital parts of the project. These cables would be installed in a staggered formation so they would not all be in the same horizontal plane. The upper cables, which would suffer any initial impact, would have tough armor-plated "shields." Deflected bombs would tumble downward against each successive cable grid and detonate before ever hitting the dam.

Hansen sent his proposal to Ickes on July 14, 1940, and asked for a meeting with him to discuss the plan and present sketches and drawings. On September 12, 1940, Hansen got a letter from Page asking for the sketches and drawings as soon as possible.

By then a number of incidents had upset Hansen, and he responded in a long letter to Page that he had destroyed the sketches. Also, Hansen had traveled to Washington at his own expense in hopes of meeting with Ickes and was "put off" for three days, then told that Ickes was too busy to see him and was not interested in matters of national defense.

Acting Reclamation Commissioner Bashore then sent a telegram to Hansen, urgently requesting the sketches. This time the response from the artist was much terser. He wrote on September 22, 1940: "You folks have some nerve to wire me for my time and efforts" when he was still awaiting a final payment of five hundred dollars from Reclamation. At the end of October 1940, reference is made to awaiting Hansen's recommendations in a letter from Stimson to Ickes. No final report from Hansen was found among the Archives records, and his concept never went beyond words.

Although the War Department had been unwilling to provide armed guards or ammunition to assist in the protection of the dam, it did send an army officer there to assess the adequacy of the security in place. In September 1940, Col. E. A. Stockton, Jr., conducted the review and submitted a report. Although Reclamation had done much to strengthen protection of the dam from sabotage, Stockton recommended additional measures. Commissioner Page, upon reviewing the findings, concurred that extra vigilance at Hoover Dam was mandatory: "As I view it, we have a public trust at Boulder Dam greater than that represented by the ordinary public works. The dam is a symbol as well as a vital factor in the water and power supply of the Southwest." Page felt that due to the dam's special significance, the public had a right to visit it, and everything possible should be done to keep it open. More than half a million people visited the dam each year. Page authorized immediate implementation of most of Stockton's suggestions including augmenting the number of rangers (who by then totaled thirty-six), providing them with more effective arms, completing the protective fencing project, constructing a concrete powder house, and installing gates across the main Arizona and Nevada approaches to the dam. Page recommended further study of Stockton's proposal to install a deep submerged net to protect the intake towers from subsurface bombs or torpedoes.

In December 1940 the army announced that it planned to establish a cantonment with a force of some eight hundred men in or near Boulder City. Speculation ran high that the purpose of the post was to provide protection for Hoover Dam. Rumors also flew that the army intended to enforce martial law in the community—news that was not well received by the residents or by the Interior Department. Those fears were put to rest when Stimson informed Ickes in January 1941 that the War Department had no plans whatsoever to establish martial law. A few months later, on April 24, an article appeared in the Washington Post with the headline, "Army to Send 850 to Guard Boulder Dam." In fact, the military had no intention of assuming protection of Hoover Dam and the power plant. The new military police camp at Camp Sibert would be used primarily as a training facility. The War Department made it very clear that the military police would not substitute for Reclamation's ranger service but might be available to assist at times. In July 1941 Reclamation and the U.S. Army approved an agreement whereby the latter would patrol the switchyards adjacent to the dam, the Boulder City water system, and other outlying facilities. The army also offered to provide a convoy service to accompany vehicles across the dam. It was understood that the troops might be called away on very short notice.

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The top of Hoover Dam, with transmission wires on the left, by Ansel Adams.

Upon instructions from the President, in February 1941, the Federal Power Commission prepared a secret memorandum outlining measures to be taken to protect the U.S. power supply against hostile acts. The memo also recognized that because of the unlimited number of methods that could be used to sabotage equipment, and the varying circumstances at different power plants, it would be impossible to cover the problems of sabotage and air-raid protection in an exhaustive manner.

Following this broad evaluation of security concerns, the Federal Power Commission conducted intensive surveys at major power facilities. In May 1941 the agency completed its assessment of protective measures at Hoover Dam power plant. While the inspecting engineer found the plant "reasonably well protected" by lighting, fencing, a guard force of sixty men, and the natural topography of the deep canyon, he made nineteen recommendations for improving security. The first two were to prohibit visitors from entering the plant and automobiles from parking on the dam or roadway above the power plant. Other suggestions addressed increased lighting, fencing, alarm systems, and other barriers. The final recommendation was to install fog nozzles at various places around the dam, a measure that would later receive substantial scrutiny by Reclamation. Over the next three years, the Federal Power Commission conducted six supplemental reviews of security at Hoover Dam.

On September 17, 1941, the secretary of the interior approved "Regulations Governing the Protection of Structures" on Reclamation projects in operation or under construction. Different levels of protection were specified depending on the national, state, or local significance of the facility. Hoover Dam fell under the definition of a Class I structure "of paramount importance to and irreplaceable in operations of national defense by reason of major power supply." The highest level of protection was reserved for these facilities and consisted of "adequate and complete protection of all vulnerable features at all times by a sufficient number of armed guards."

Despite the escalating war and the ever-increasing possibility of direct U.S. involvement, visitors continued to be allowed to tour Hoover dam and power plant, although under tighter restrictions.

The bombing of Pearl Harbor changed that immediately. On December 7, 1941, E. A. Moritz, director of power at Hoover Dam, sent a telegram to Page stating that "Effective 5 pm today Boulder power plant has been closed to visitors and flood lights extinguished. All persons and cars will be checked in at boundary gates in Nevada and Arizona and cars convoyed across the dam. Request all unauthorized flying over this area be prohibited." The next day, Page closed the dam to all visitors except those on official business. In a press release, he said, "I regret exceedingly that it has been necessary to close this great public work to the public, but the step obviously now is necessary."

Also on December 8, Ickes sent a letter to Stimson requesting army assistance in guarding major facilities of the Department of the Interior, in particular Boulder, Grand Coulee, and Shasta dams. He wrote, "I assume that the present conditions constitute circumstances justifying such action by the Army." The army cooperated and established additional posts in Boulder City, at the switchyards, and at a few other key places in the vicinity of the dam. Reclamation officials felt that the dam was still not safe against air attacks, however, and that antiaircraft guns and fighter planes were essential to protect the facility. Although the army did not share Reclamation's concern about the threat of an aerial bomb attack, Stimson wrote to Ickes on March 14, 1942, that he intended to designate Boulder Dam a prohibited zone that would deny right of entry to within one mile of the dam to enemy aliens and "other classes of persons so designated" by the commanding general of the Western Defense Command and Fourth Army. Stimson did not elaborate on whether he intended the military to enforce this prohibition.

Just four months later, Moritz registered a complaint that none other than the military was violating safety precautions. On July 6, 1942, Maj. Gen. George S. Patton, Jr., flew dangerously low over the dam at about five hundred feet. Moritz wrote to Chief Engineer S. O. Harper, "It appears that if the Army feels any responsibility for the safety of the project and for continuity of power service, it should be the first to frown upon such hazardous acts." Moritz noted that the local army officers had always cooperated with Reclamation and also did not condone Patton's behavior. Harper forwarded Moritz's letter to the army, adding his own objection to the incident. The lack of adequate control of air traffic over Hoover Dam continued to be an issue between Reclamation and the military over the next year.

As in the past, private citizens wrote letters to Reclamation expressing deep concern for the safety of the dam. Chester Versteeg with Pacific Mutual Life Insurance Company provided the following recommendation just days after the attack on Pearl Harbor: "Because of the real danger of one or more enemy suicide planes loaded with powerful explosives following up the gorge of the Colorado River and striking horizontally against and destroying the Power Plants at Boulder Dam, I urge the immediate construction of a strong chain net or group of wire cables approximately 200 yards below the dam and from the river surface to the height of the dam." The sheriff of Nevada City, California, contacted the FBI to express his opinion that Hoover Dam was not properly guarded. His concerns made it to Ickes. Ickes also received notification from FBI Director Hoover that an informant had reported to him a number of safety breaches at the dam. In response, Ickes sent a team to investigate the alleged conditions.

During the summer of 1942, Reclamation continued its own exploration of measures to protect the dam from possible air raids. The previous year it had begun to evaluate, with assistance from the Corps of Engineers, the strength of the powerhouse roof against bomb attacks. In 1942, models of the structure were built at the Aberdeen, Maryland, Proving Ground and then fired at to test the vulnerability of the roof. Other Reclamation investigations focused on the possibilities of protection by camouflage and chemical smoke screens.

Learning that the army was conducting its own similar studies at Bonneville Dam in Washington State, Reclamation drafted a letter for Ickes to send to Stimson requesting that the army install and maintain "camouflage, smokescreens, and other protective measures at Boulder, Grand Coulee [Washington] and Parker Dams [straddling Arizona and California]." Reclamation officials were becoming increasingly frustrated by the army's unwillingness to clearly state where the protection of Hoover Dam fit into its plans to defend the West Coast in the event of aerial bombardment. The response from the army at the end of October 1942 helped to clarify its position, although it was disappointing to Reclamation: its three major dams of concern were outside a two-hundred-mile radius of the West Coast and therefore would not receive smoke protection. The army did agree to conduct surveys at the three dams to determine requirements for future possible installations. Months would pass before this was completed.

In the meantime, as the war raged on, Reclamation's concern for the vulnerability of its facilities continued to mount, prompting the agency to investigate on its own the use of smoke screens and camouflage. In February 1943, a Reclamation engineer, E. H. Heinemann, attended a demonstration of smoke-generating apparatus at the Norfolk, Virginia, Naval Air Station. Circling above the test area in a small plane, Heinemann observed the artificial fog completely envelop and obscure miles of ground. He concluded that the screen was very effective and could be useful in protecting the power installations at Hoover, Grand Coulee, and Parker. That same month, a fascinating report on the usefulness of camouflage to protect Reclamation structures was submitted by "color consultant" Allen T. True. For a second time, one of the artists engaged in the original design of Hoover Dam became involved in safeguarding it. True, a Colorado painter who specialized in depicting Western and Native American themes, had executed the imaginative Indian designs for the terrazzo floors of the powerhouse and lobby of the elevator towers at the top of the dam.

During the summer of 1942, True had attended a camouflage training course conducted by the Corps of Engineers in Virginia. From his experiments at Reclamation's Denver laboratories, True concluded that various degrees of camouflage would be effective but only in combination with a smoke screen. To help conceal the dam from planes overhead, True recommended various treatments including "toning down" the dam and spillways by painting them with bold, simple masses of colors in larger areas and darker tones than would seem acceptable. To create the illusion of water above and below the dam being connected, True suggested installing a thin sheet of water on the horizontal planes such as the roofs of the power plant and on the dam roadway.

Probably the most intriguing element was the proposal to build a "dummy" dam downstream from the real one as a decoy. The decoy, three-fourths the size of the real one and made of "garnished wire," would be painted various colors and different textures to simulate the concrete and the rocks of the cliffs. True's decoy study never went beyond a fascinating proposal tucked away in a forgotten file. Finally, in the spring of 1943, the War Department's Office of Chemical Warfare Service conducted its study on the feasibility of employing large-area smoke screens to protect Hoover, Grand Coulee, and Parker dams. Allen True was designated to represent Reclamation in carrying out the investigations. After accompanying a representative of the Chemical Warfare Service to the three dams, True wrote a memo to Chief Engineer Harper saying that he felt the trio of structures were the most attractive in the West to bomb because they supplied more than half of all the electric power used by war industries on the West Coast. Planes were still flying over these plants day and night with little or no controls in place. True recommended that Ickes take the matter of adequate protection directly to Stimson.

True's suggestion was taken seriously, and matters came to a head when Ickes sent a letter to Stimson on April 26, 1943. He began with, "what we would still like to obtain, is a statement of policy on the part of the War Department as to what assistance we can expect from the Army in the event of enemy air raids." Ickes' concluding paragraph was blunt: "Because the loss of Boulder, Parker, and Grand Coulee power plants would be a fatal blow to war production on the West Coast, because the Department of the Interior does not have the facilities for their protection from air assault, and because there is a need for the coordination of measures for passive defense, I request that the Army assume the entire responsibility for their protection."

It took Stimson more than a month to reply. "The importance of these dams as power installations has been fully recognized by the War Department," he wrote. "The threat at this time is considered to be limited to nuisance or sporadic air raids by light airplanes released from submarines, or at most, medium bombers launched from carriers. . . . To make such attacks an impossibility would require a much greater air force on this continent than can properly be spared from offensive action against the enemy." Stimson wrote that the chances of intercepting Japanese bombers en route from the coast to the dam were excellent. His concluding paragraph was equally as straightforward as that of Ickes, "Under the circumstances I believe that the acceptance of the risk involved is justified and that assumption by the Army of responsibility for passive protection of the dams in question is not necessary."

For the remainder of the war, Reclamation was on its own in protecting Hoover Dam.

More bad news from the military followed. In early September 1943, Reclamation was notified that the small number of army guards stationed at Hoover Dam and the convoy service that the army provided would be discontinued as the soldiers were being shipped elsewhere. Assistance from the FBI was also not forthcoming. In November 1943, J. Edgar Hoover turned down a request from recently appointed Commissioner Bashore that the FBI conduct another survey of the protective measures at Hoover Dam. Bashore had made the appeal following repeated charges by one of the rangers that security at the dam was inadequate due to a number of reasons, including laxness on the part of the ranger staff. By then, it was indeed becoming difficult to recruit competent men; morale was low, and turnover was high due to the shortage of housing, the high cost of living in Boulder City, and the attraction of higher paying jobs in the defense industry.

Dismissed by the FBI, Reclamation turned to U.S. Army Intelligence, which conducted a security survey. The report, prepared in January 1944 by Major Owen of the Continuous Security Branch, Ninth Service Command, concluded that many of the ranger's charges, which he made to an array of politicians, including the President and other top officials, were without merit or exaggerated, while others were justified, either wholly or in part. In a letter to Ickes defending Reclamation's continuous efforts to ensure adequate security at Hoover Dam, Bashore wrote, "While I realize the constant danger of sabotage to a project of the importance and vulnerability of Boulder Dam, it is significant that there has been no incident there."

Just when it appeared that security matters had calmed down at Hoover Dam, another alleged sabotage plot surfaced. This time the ostensible conspirators were Japanese and Chinese, operating through two Mexican agents. The news reached the press and on April 17, 1944, headlines in the Boulder City Evening Journal announced "Scheme to Dynamite Boulder Dam Nipped by San Diego Federals Today." The FBI had arrested Andres Sanchez, a Mexican laborer, on charges of attempting to wreck a railroad train in southern California. The newspaper recounted that Sanchez admitted to being involved in a plot to dynamite Hoover Dam. Just days later, the FBI Director Hoover wrote to Ickes to notify him that the sabotage plot had been investigated further and found to be entirely fabricated. The FBI informant confessed that there was no truth at all to the rumor of a plan to blow up Hoover Dam.

As the war turned in favor of the Allies, the intense security concerns at Hoover Dam lessened. The fear of sabotage abated, and the investigations into the "loyalty and trustworthiness" of project employees were discontinued. Bashore felt strongly that Reclamation facilities should allow visitors, subject to rules based on "facts, reasonable precautions, logic, equity, and practicability." To Bashore, offering the public a firsthand opportunity to view Reclamation projects was of utmost importance to acquaint them with the agency's purposes and accomplishments.

As conditions started to return to normal in 1946, the matter of law enforcement was dealt with in a few paragraphs in the project's annual report. Reclamation's ranger force continued to maintain law and order in Boulder City and the vicinity of the dam. A monthly average of twenty-nine rangers and seven watchmen were on duty, patrolling the city, checking traffic, watching for suspicious characters, and maintaining the peace on Bureau of Reclamation lands.

The events of September 11, 2001, rekindled fears of attack on Hoover Dam. Newspaper articles reminiscent of those published during World War II raised the specter of possible sabotage and the need for increased security. Once again, safeguarding one of the country's most well-known and recognized landmarks became a matter of national security.

Christine Pfaff is a historian with the U.S. Bureau of Reclamation in Denver. She researches and writes about water development and irrigation projects throughout the West.

Note on Sources

Information for this article was almost entirely drawn from records housed at the National Archives and Records Administration - Rocky Mountain Region, Denver, Colorado. See Record Group 115 (Bureau of Reclamation), Entry 7, general correspondence and project (Colorado River Project) correspondence files for the years 1930–1945. Reclamation's monthly journal Reclamation Era also provided material on the sequence of events relating to the establishment of law enforcement provisions at Hoover Dam. Information on the artistic achievements of Oskar Hansen and Allen True at Hoover Dam can be found in Reclamation Era (see January and February 1936 volumes for articles on Allen True) and a brochure entitled "Sculptures at Hoover Dam" published by the Bureau of Reclamation in 1978. Learn more about the history of Hoover Dam and the Bureau of Reclamation at

The author wishes to thank the NARA staff in Denver; Roy Wingate, records manager in Reclamation's Denver office; and Emme Woodward, museum specialist, and Karen Cowan, both with the Bureau of Reclamation in Boulder City, Nevada, for all their assistance.


* Both the names Hoover and Boulder have been used for the dam. In 1930, Interior Secretary Ray Wilbur announced that the dam would be called Hoover Dam, and Congress affirmed the name to honor the then-President of the United States. After Roosevelt took office in 1933, the dam, which was actually built in nearby Black Canyon, was frequently called Boulder Dam or Boulder Canyon Dam allegedly because Roosevelt's Interior Secretary, Harold Ickes, did not like Hoover. Therefore, when quoting documents from the time, Boulder Dam is often used. In April 1947, an act of Congress signed by President Truman officially confirmed the name as Hoover Dam.


Articles published in Prologue do not necessarily represent the views of NARA or of any other agency of the United States Government.