Construction Timeline


Hernando de Alarcon is the first European to see the Colorado River


James O. Pattie, trapper from St. Louis, and his companions explore Black Canyon


John C. Fremont begins his explorations of the Colorado


After crossing the Colorado River Basin, Mormons settle in Salt Lake Valley


Dr. O.M. Wozencraft begins dreaming of irrigating the Imperial Valley by channeling waters from the Colorado through the Salton Sink.


Major John Wesley Powell begins 1000-mile long expedition along the Colorado from Green River, Wyoming to the mouth of the Virgin River in Nevada.


The engineer C. R. Rockwood visits Salton Sink and revitalizes Wozencraft’s plan of irrigating the Imperial Valley through the Salton Sink. Based on his plans, he organized the Colorado River Irrigation Company.


After the failure of the Colorado River Irrigation Company, the California Development Company forms with C.R. Rockwood in charge of engineering and construction.


The Colorado Development Company begins construction on the Imperial Canal. By 1904, 700 miles of canal supports 8000 settlers and 75,000 acres of crops.

1903 – 1906

Silt deposits begin collecting in the Imperial Canal. Through an agreement with the Mexican government, a bypass was cut right past the Mexican border. After intense winter flooding, the temporary diversion works at the Mexican head gate failed and the river ran unchecked through the Imperial Canal. The Imperial Valley was flooded resulting in dramatic loss of crops. Salton Sink, long time reservoir of Colorado floods, became the Salton Sea and later developed into a major recreation and wildlife area. The Southern Pacific Company closed the break in 1906.

1906 – 1907

The Colorado breaks through the canal on two more occasions, once again flooding the Imperial Valley. Under orders from president Roosevelt, the break is closed using government funds.


The Imperial Irrigation District, through the Southern Pacific Company, purchases California Development Company properties in the Imperial Valley for 3 million dollars.


Federal government begins investigations of the Imperial Valley and the possibility of building a canal that would run only through the United States.


The All-American Canal bill is introduced in Congress. The bill called for the construction of the canal as well as all related works to be built entirely within the United States.


The Fall-Davis report is issued, detailing the preliminary investigations as to where the dam would be built. Later that year the Colorado River Compact is signed, providing for the apportionment of water among the Basin States (Arizona, California, Colorado, Nevada, New Mexico, Utah, and Wyoming).


Congressman Phil Swing introduced bill for the authorization of the Boulder Canyon Project Act. Senator Hiram Johnson simultaneously introduced a companion bill. This was the fourth and final of the “Swing-Johnson” bills.


The latest Swing-Johnson bill is approved by both houses and President Coolidge. Various engineers and scientists are commissioned to study the proposed dam site in Boulder Canyon.


President Herbert Hoover declares the Boulder Canyon Project Act effective.


Secretary of the Interior begins construction of the dam by driving a silver spike near the dam site.