An image showing aerial view of Hoover Dam. Note: Boulder Dam was officially renamed Hoover Dam in 1947.

An image of a collage of photographs and postcards of Hoover Dam. Note: Boulder Dam was officially renamed Hoover Dam in 1947.

One of the Mack trucks in front of the upper portal of Diversion Tunnel #2. This truck has 9 cubic yards capacity. Note the steel canopies over the driver's heads on all the trucks. Jan. 28, 1932.

A flashlight photograph of the interior of one of the diversion tunnels. The drilling jumbo is working at the tunnel face. The 12' by 12' top-heading can be plainly seen. January 28, 1932.

Drilling jumbos (aka Williams Jumbo) mounted on the back of a truck for starting construction of lower portal No. 4, Arizona side of Black Canyon. 9-26-31. (This first wood-frame jumbo was experimental - the jumbos later were steel pipe)

Looking up Black Canyon from a point below all the lower portals, showing the Government pumping plant (lower left), the Six Companies' compressor plant (middle left), the location of the lower portals, & the highway loop above the canyon wall (upper center) - 7/30/31.

p.16 #1074 Scaling down canyon wall, in excavation for intake tower on Nevada side. Apr. 1, 1932. p.16 #1073 Close-up of No.1074 to the left. Workmen are 700 feet above river. Apr. 1, 1932.