Black and white image of Secretary of the Interior, Dr. Ray Lyman Wilbur, on a tour of inspection at Hoover Dam. It was under Dr. Wilbur's supervision that the Boulder Canyon Project was commenced. In the background the concrete form used in lining the 50-foot diversion tunnels at the outlet portal of Diversion Tunnel No. 2 can be seen. Note: Boulder Dam was officially renamed Hoover Dam in 1947.

Black and white image of a caravan of over 500 automobiles on their way to visit the Boulder Canyon Project in Boulder City. The passengers were possibly headed to view the diversion of the Colorado River. Note: Boulder Dam was officially renamed Hoover Dam in 1947.

Black and white image of the Nevada spillway at Hoover Dam under construction. Note: Boulder Dam was officially renamed Hoover Dam in 1947.

Black and white image of Dr. Ray Lyman Wilbur, Secretary of Interior, naming the Boulder Dam (name officially changed to Hoover Dam in 1947) at a ceremony celebrating the beginning of work on the Boulder Canyon Project and the beginning of the construction of Union Pacific Railroad from Boulder Junction (Bracken Junction) to the dam site.

Black and white image of Black Canyon during the construction of Hoover Dam. Cable way elevators which transported the fathers of Hoover Dam to and from work can be seen, along with a pilot house on the Nevada side of the canyon. Note: Boulder Dam was officially renamed Hoover Dam in 1947.

Black and white image of excavation activities at the bed of Hoover Dam. High scalers can be seen displaying their clinging skills on the walls of the Black Canyon. Note: Boulder Dam was officially renamed Hoover Dam in 1947.

Black and white image showing a downstream view of the Hoover Dam construction site from the lower slope of the upper cofferdam. The excavation for the base of the Nevada intake towers can be seen in the upper right. Note: Boulder Dam was officially renamed Hoover Dam in 1947.