Diagram of log holes, Hoover (Boulder) Dam. Note on back: "Copy of Bureau of Reclamation diagram. Stuck some drills in river bottom and recovered them after the river was diverted. - W. A. Davis, 1992."
Panoramic image of Hoover (Boulder) Dam construction, early evening view, November 1933. Lights line the canyon walls as workers proceed with construction. Bright white light in the sky may possibly be a full moon.