Looking downstream at cofferdam and diversion tunnels.

Cofferdam (upper one), 1/4 - 1/2 mile upstream from Dam site. Dec. 25, 1932. Note on back: ""Electric Marion steam shovel on top of cofferdam. May have used shovel to lay down metal grating. - W. A. Davis.""

Aerial view of canyon basin just before 'drying up'. Workers are preparing to dry up bottom of canyon.

Aerial view of Colorado River drying up after cofferdam was built.

Working at Hoover (Boulder) Dam. The machinery shown include a water pump and power shovel. Note on back: "Not taken by W. A. Davis. That day the river came up and flooded tunnel on Arizona side. This shot shows pumpking the water out with a large sump pump. - James J. Hester, W. A. Davis' son-in-law, 1992."

Bottom of Black Canyon before Hoover Dam construction. Showing keys in wall, and adit tunnel entrance.

View of Black Canyon basin, almost drained completely down to bedrock.