Airplane and four unidentified individuals (probably Las Vegas)

Illustration of Arrowhead Trail on a postcard with the caption, "Crossing the desert, Arrowhead Trail." A car is seen driving through a blooming desert.

Postcard with an illustration of a dry lake in front of mountains. The typed caption reads: "A dry lake near Boulder Dam."

Postcard with an illustration of Colorado River looking upstream between mountains. The typed caption reads: "Colorado River, looking upstream, Boulder Damsite in 1931."

Illustration on a postcard of giant tunnels creating diversions for the Colorado River during the construction of Hoover Dam. The caption reads: "Diverting the Colorado River through giant tunnels."

Postcard with an illustration of Hoover Dam. The caption reads: "Boulder Dam, as it will look when completed, Colorado River."

Illustration of Boulder Dam, later called Hoover Dam, construction. Caption reads: "A close-up, showing construction detail, Boulder Dam, Colorado River."