Hoover Dam is an arch concrete structure located on the Colorado River in Black Canyon at the Nevada/Arizona state line. Hoover Dam was dedicated on September 30, 1935, by President Franklin Delano Roosevelt. Prior to the dedication of Hoover Dam, the structure was already assigned as part of US Route 466 and US Route 93. This blog will examine the history of highway designations over Hoover Dam and serve as the fourth entry on the Legacy of US Route 466 series.
Part 1-Part 3 of the US Route 466 Legacy Series can be found below:
Legacy of US Route 466 Part 1: California State Route 46
Legacy of US Route 466 Part 2: Tehachapi to Bakersfield
Legacy of US Route 466 Part 1: California State Route 46
Legacy of US Route 466 Part 2: Tehachapi to Bakersfield
Part 1; the history of US Route 466 and US Route 93 over Hoover Dam
The site of Hoover Dam is located along the Colorado River at the Nevada/Arizona state line in Black Canyon. The origin of Hoover Dam can be traced to the signing of the Colorado River Compact on November 24, 1928. The Colorado River Compact was an agreement between the Southwest States along the Colorado River watershed which governs water allocations.
Black Canyon was desired as a site to construct a dam which would impound a large reservoir. Initial proposals for construction of a dam at Black Canyon were stalled by the collapse of the St. Francis Dam north of Los Angeles in San Francisquito Canyon on March 21, 1928. St. Francis Dam was a similar design as what was proposed for Black Canyon which brought concerns over the safety into question. Despite the difficulties on Federal legislation then President Calvin Coolidge signed the Boulder Canyon Dam Project Act on December 21, 1928.
The Bureau of Reclamation eventually settled upon a 727-foot-tall arch concrete dam. The design of Boulder Dam would narrow 45 feet at the top which would permit a modernized highway to be constructed. The design of Boulder Dam and the highway atop the structure can be seen in a 1930 Bureau of Reclamation planning document.
Prior to the construction of Boulder Dam, no direct highway link between Las Vegas, Nevada and Kingman, Arizona existed. The quickest route south of Las Vegas followed the pre-Silver Lake Cutoff alignment of the Arrowhead Trail (future US Route 95) to US Route 66 in Bannock, California. From Bannock traffic could follow US Route 66 eastward into Arizona towards Kingman.
The 1929 Nevada Department of Highways presents the early Arrowhead Trail south of Las Vegas to the California state line as part of Nevada State Route 5. Within California the early Arrowhead Trail from the Nevada state line to US Route 66 in Bannock was not under state maintenance until it became part of Legislative Route Number 146 in 1933.
During June 1933 the California Division of Highways petitioned the American Association of State Highway Officials (then AASHO, now AASHTO) for an extension of US Route 64 west of Raton, New Mexico to Morro Bay, California. The extension of US Route 64 was not considered ideal by AASHO due to proposed routing including a lengthy multiplex of US Route 66 from Santa Fe, New Mexico to Barstow, California. An alternate proposed routing of US Route 64 in New Mexico did little to mitigate the lengthy multiplex of US Route 66 in Arizona. The proposal to extended US Route 64 was to be reviewed by the AASHO Executive Committee during their October 1933 meeting.
During their August 1933 meeting AASHO suggested US Route 466 to the California Division of Highways as an alternative to the lengthy extension of US Route 64. US Route 466 was initially proposed as originating in Barstow, California and terminating at Morro Bay. The Division of Highways via telegram to AASHO dated August 10, 1933, expressed that such a short US Route located entirely in-state would not provide the same utility as their US Route 64 extension proposal.
During the October 1933 AASHO meeting a compromise was reached which brought US Route 466 into existence. US Route 466 would begin at US Route 66 in Kingman, Arizona and travel northwest to the site of Boulder Dam at the Nevada state line. Within in California, US Route 466 would retain the same Barstow-Morro Bay alignment desired by the California Division of Highways for their US Route 64 extension proposal.
The first description of US Route 466 in Nevada is a letter dated November 14, 1933. In said letter the Nevada State Highway Engineer describes the routing of US Route 466 to the AASHO Executive Secretary. The origin point of US Route 466 is stated to be from the site of Boulder Dam westerly via Nevada State Route 26 and Nevada State Route 5 to Las Vegas. From Las Vegas, US Route 466 multiplexed US Route 91 along Nevada State Route 6 to the California state line at Primm. US Route 466 would continue to multiplex US Route 91 in California to Barstow where it would branch off towards Morro Bay.
The first concrete poured for the superstructure of Boulder Dam was laid on June 6, 1933. Given Boulder Dam was far from complete by the time US Route 466 came fully into existence the highway initially had a gap. The gap in US Route 466 could functionally be bridged by the temporary Boulder Dam Ferry over the Colorado River. The Boulder Dam Ferry can be seen in a 1932-era photo from the Mohave Museum of History and Arts housed on the Arizona Memory Project webpage.
The Boulder Dam Ferry can be seen on the 1933 Midwest Map Company Highway Map of Arizona. The location for the landing of the Arizona side of the Boulder Dam Ferry appears to be likely Willow Beach.
The 1935 Nevada Department of Highways Map is the first to display US Route 466 in the state. Nevada State Route 26 is shown to be truncated as running between Nevada State Route 5 and Boulder City. Nevada State Route 42 is shown have replaced Nevada State Route 26 east of Boulder City to the Boulder Dam construction site.
During May 1935 the Arizona State Highway Department and Nevada Department of Highways submitted a joint request to AASHO to extend US Route 93 from Glendale, Nevada to Kingman, Arizona by way of Boulder Dam.
The completed Boulder Dam was dedicated by then President Franklin Delano Roosevelt on September 30, 1935. The highway over Boulder Dam carrying US Route 466 and US Route 93 was from the outset maintained by the Bureau of Reclamation. US Route 466 and US Route 93 appear multiplexed over Boulder Dam on the 1937 Gousha Map of Nevada.
The name "Boulder Dam" had historically been contentious due to the structure more commonly having been referred to as "Hoover Dam." On September 17, 1930, during a ceremony starting construction of the rail line to the Boulder Dam site, Secretary of the Interior Ray Wilbur had referred to the structure as "Hoover Dam." Hoover Dam had been referenced by name in numerous legislative bills which funded construction. Congress formally passed legislation in 1947 which changed the name of the structure to Hoover Dam.
On February 15, 1956, the Nevada State Highway Engineer in a letter to AASHO advising that six copies of an application to establish US Route 66 Alternate to Las Vegas had been submitted. The Nevada State Highway Engineer noted the State of California agreed to sign US Route 66 Alternate if approved and they were anticipated to submit their own like request to the AASHO Executive Committee.
The actual submission to by the Nevada State Highway Engineer was made on February 27, 1956. The proposed US Route 66 Alternate would have originated from mainline US Route 66 in Kingman Arizona and followed a multiplex of US Routes 466 and US Route 93 to Las Vegas, Nevada. From Las Vegas, Nevada the proposed US Route 66 Alternate would have multiplexed US Routes 91 and US Route 91 back to mainline US Route 66 in Barstow, California. The rationale for US Route 66 Alternate being established was that it was desired by the communities along the prospective highway to obtain access to an alternative alignment of US Route 66.
Below a description of proposed US Route 66 Alternate can be observed. Proposed US Route 66 Alternate is stated to be 259 miles long.
The Arizona State Highway Engineer affirmed concurrent agreement with the US Route 66 Alternate proposal to the AASHO Executive Secretary in an undated Western Union telegram.
The AASHO Executive Commitee considered US Route 66 Alternate during the June 27, 1956, meeting and ultimately denied the request.
US Route 466 was approved for truncation from Morro Bay to California State 127 in Baker by the AASHO Executive Committee during June 1964. This truncation would see US Route 466 terminate on Baker Boulevard at the intersection with California State Route 127/Death Valley Road. The truncation of US Route 466 to Baker did not impact the existing routing in Nevada nor Arizona but it did leave it fully multiplexed with other US Routes.
The states of Nevada, Arizona and California filled a joint request to AASHO to eliminate the remaining portion of US Route 466 on November 22, 1971. The AASHO Executive Committee approved the deletion of US Route 466 on December 4, 1971. The deletion of US Route 466 left US Route 93 as the only signed route over Hoover Dam.
The 1972 Official Highway Map of Nevada displays US Route 93 as the lone route crossing Hoover Dam.
During 1995 the entirety of US Route 93 south of Las Vegas was selected as part of the CANAMEX corridor which would comprise Future Interstate 11. During March 2001 the Federal Highway Administration issued a record of decision favoring a Hoover Dam Bypass bridge south of the structure via Sugarloaf Mountain.
Following the September 11, 2001, terrorist attacks the Bureau of Reclamation banned commercial traffic over Hoover Dam. This measure required a lengthy detour for Las Vegas-Kingman commercial traffic via Arizona State Route 68, Nevada State Route 163 and US Route 95.
Construction for the approaches to the Hoover Dam Bypass Bridge would begin during 2003 followed by the span itself during 2004. During late 2004 the Hoover Dam Bypass Bridge was officially named Mike O'Callaghan-Pat Tillman Bridge. Mike O'Callaghan is a former governor of Nevada who served during 1971-79. Pat Tillman is a former Arizona Cardinal Safety who left his National Football League career to enlist in the United States Army after the terrorist attacks of September 11, 2001. Tillman was killed by friendly fire while serving in Afghanistan during 2004.
Mike O'Callaghan-Pat Tillman Bridge opened to traffic on October 14, 2010, as a replacement for the existing alignment of US Route 93 over Hoover Dam. Upon Hoover Dam being bypassed portions of the former routing approaching the structure became Nevada State Route 172 and US Route 93X in Arizona. The roadway atop Hoover Dam remained under the maintenance of the Bureau of Reclamation.
A brochure from the Hoover Dam Bypass circa 2009 details the opening of the Mike O'Callaghan-Pat Tillman Bridge and realignment of US Route 93.
The Nevada Department of Transportation and Arizona Department of Transportation submitted a joint request to AASHTO for the relocation of US Route 93 onto the Mike O'Callaghan-Pat Tillman Bridge on September 3, 2010.
On May 12, 2014, the Nevada Department of Transportation submitted a request the American Association of State Highway and Transportation Officials to designate Interstate 11. The request specified the Interstate 11 corridor was to include the planned Boulder City Bypass between the Arizona state line and Interstate 215. Interstate 11 in the submission would fully overlap and multiplex US Route 93 south of Interstate 215 and replace approximately 5 miles of Interstate 515. The submission noted the Boulder City Bypass was expected to be open during September 2018.
The application by the Nevada Department of Transportation requesting an Interstate 11 designation along US Route 93 south of Interstate 215 to the Arizona state line was approved by the American Association of State Highway and Transportation Officials on May 29, 2014. During May 2017 the American Association of State Highway and Transportation Officials approved an application for the surface segment of US Route 93 through Boulder City on Boulder City Highway to become the US Route 93 Business Route.
Construction of the Boulder City Bypass would conclude in two Phases. The Phase 1 corridor of the Boulder City Bypass was from Foothills Drive in Henderson south through Railroad Pass to the new Boulder City interchange. The full Phase 1 segment of the Boulder City Bypass opened to traffic on May 23, 2018.
Phase 2 of the Boulder City Bypass opened on August 9, 2018. The Phase 2 corridor of the Boulder City Bypass included the entire freeway between the Boulder City interchange to Nevada State Route 172. The Interstate 515 signage from Railroad Pass north to Interstate 215 was fully replaced with Interstate 11 signs by March 2019.
As of the publishing date of this blog the Nevada Department of Transportation has not pursued making the extension of Interstate 11 official with the Federal Highway Administration or the American Association of State Highway and Transportation Officials. The current Federal Highway Administration Interstate highway log depicts Interstate 11 as 22.6 miles. To date, Arizona has not pursued any official designations for Interstate 11 south of the Mike O'Callaghan-Pat Tillman Bridge. Presently Interstate 11 currently ends in the center of the Mike O'Callaghan-Pat Tillman Bridge at the Arizona state line.
Part 2; a drive along former US Route 466 and US Route 93 atop Hoover Dam
From the Nevada side former US Route 466/US Route 93 over Hoover Dam can be accessed from Interstate 11/US Route 93 Exit 2 towards Nevada State Route 172. Nevada State Route 172 comprises the 1.351 miles of former US Route 466/US Route 93 from Interstate 11 to the boundary of the Bureau of Reclamation lands of Hoover Dam and the Lake Mead National Recreation Area.
Beyond a Bureau of Reclamation checkpoint and walkway from former US Route 466/US Route 93 to the Mike O'Callaghan-Pat Tillman Bridge can be found. Hoover Dam, former US Route 466/US Route 93 and Lake Mead are easily visible from the walkway atop Mike O'Callaghan-Pat Tillman Bridge. Mike O'Callaghan-Pat Tillman Bridge itself is a concrete-steel arch composite span which is 1,900 feet long.
Various photos of items from the Mike O'Callaghan-Pat Tillman Bridge seen circa 2018.
The Arizona Department of Transportation defines US Route 93X as being 2.13 miles. The origin point for US Route 93X is referenced as the state line atop Hoover Dam on Bureau of Reclamation maintained road. The Arizona Department of Transportation maintained US Route 93X begins at mile 1.01. The eastern terminus of US Route 93X is at mainline US Route 93 at the Exit to Kingman Wash Road.
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