An artist's rendering of Boulder Canyon. Text on front of postcard: "Hoover Dam site, Boulder Canyon, looking downstream." Text on back of postcard: "Work is rapidly progressing on the new Hoover Dam, thirty miles southeast of Las Vegas. This tremendous project will cost the government in excess of $165, 000, 000.00 and will take about eight years to complete. The dam site is where the river disappears in the center of the picture. Arizona is on the left, Nevada on the right. Within a decade, the parched desert lands to the north will be washed by the waters of the largest man-made lake in the Western Hemisphere, impounded by the Hoover Dam, the greatest structure since Cheops."

31.1 The Rio Colorado in Yuma, Arizona.; 31.2 Work and Beddome.; 31.3 Above the dam site.; 31.4 Phelps. Back water from the Gila and Colorado River. (MISSING); 31.5 Seven unidentified men standing near a car.