In partnership with the United States government, Edison agreed to survey more unexplored territory of the Colorado River with four river survey boats, Boulder, Glen, Grand, and Marble. In 1930 Edison turned over their survey data that showed Black Canyon as the prime spot for construction of a dam capable of producing 5 billion kilowatts of power a year. Edison was contracted to supply power to the damsite and in just 225 days built the 225-mile long, 132,000 volt line from San Bernardino. On June 25, 1931, the new line to Hoover Dam Substation was delivered.
In lieu of diversion tunnels, cofferdams, penstocks, the powerhouse and a switchback to connect transmission lines were built to expand the generation of electricity beyond the damsite. October 26, 1936 marks the first day that the Hoover Dam Power Plant was put into use when it generated power for the cities of Los Angeles, Pasadena, Glendale, and Burbank, California. Electricity was delivered along the 266-mile long transmission line through which ran a world record breaking 287,000 volts of power. World War II created an even higher demand for power and a second 220,000 volt line from Hoover Dam was completed in November, 1941.
As for its part in the history of Boulder City itself, Southern California Edison Co. even managed to win a First Prize trophy in the First Annual Boulder Damboree, July 2, 3, and 4, 1949. A special exhibit of Southern California Edison’s history involving their role in creating Hoover Dam and Boulder City will be on display at the Boulder City/Hoover Dam Museum beginning February 4, 2012.