This photograph has three images. The first one, (0272_0014) reads, "Train load of gravel coming in three shay engines used for this load. Gravel comes from downstream of Boulder Canyon," as a handwritten inscription. The second one (0272_0015) that's upside down reads "March 9, 1934. New Union Pacific Train arrives at Boulder Dam." The third one (0272_0016) that's vertical shows the top workings on Boulder Dam from NV rim of Black Canyon (U.S. Bureau of Reclamation photo). It reads, "Top of dam about one form wide, everyone getting in each others way. '(0)' shows how much the slant of the dam has shortened the pours - form raisers have this one in place, waiting for carpenters to build the short side panels. (x) points out upstream face panels - form raisers nightmare, water soaked and patched up, very leery of climbing out, and straddling that lower 2x6 and start unbolting the panel. Notice the hand rails on other panels, but nothing to protect you from walking off the most thrilling fall of your life. Reeves often would (when we were safely out of sight, sitting astride a 2x6) he would sling out a bolt, and wait that long, long minute before it hit bottom. And say, 'Boy,' I'd hate to fall that far.' To be continued."

Black and white image of the Hoover Dam tunnel construction site. There are four visible bridges over the Colorado River. Note: Boulder Dam was officially renamed Hoover Dam in 1947.

An image showing a bird's eye view of Hoover Dam and vehicles on its crest from the Nevada side. The name was officially changed from Boulder Dam to Hoover Dam in 1947.

An image showing a bird's eye view of Hoover Dam and vehicles on its crest from the Nevada side. The name was officially changed from Boulder Dam to Hoover Dam in 1947.

An image showing a bird's eye view of Hoover Dam and vehicles on its crest from the Arizona side. The name was officially changed from Boulder Dam to Hoover Dam in 1947.

An image of Parker Dam on the Colorado River at the California-Arizona border, 155 miles downstream from Hoover Dam. Note: Boulder Dam was officially renamed Hoover Dam in 1947.

A postcard displaying the Visitors' Gallery within Boulder Dam leading from elevator shaft to power house. The people are gathered at the end of the hallway ready to move on to the next part of their tour.