Black and white image of several prominent figures, in front of a crowd outdoors. From left to right: Governor Balzar of Nevada; Carl Gray, President of Union Pacific Railroad Company; Ray Lyman Wilbur, Secretary of the Interior; Governor of Colorado (possibly Edwin C. Johnson). Gray is handing Lyman the first spike to be driven for the spur line to Boulder Dam. Note: Boulder Dam was officially renamed Hoover Dam in 1947.