In 1927, the Rock Island site came to the attention of the
Stone & Webster Engineering Corporation, a
Boston-based holding company that managed the Puget Sound Power & Light Company. The site was recognized for its potential to provide power for the growing electrical load in the state. On December 13, 1928, an application was filed with the
Federal Power Commission for a preliminary permit to investigate the site. This was followed by a license application submitted in June 1929 by the Washington Electric Company, a subsidiary construction corporation of Puget Sound Power & Light (now part of
Puget Sound Energy). The license was authorized on October 16, 1929, and on January 14, 1930, at the beginning of the
Great Depression, construction started on the first dam to span the Columbia River. The development of the dam took place over a period of 50 years. There were three main construction periods, each taking place about 20 years apart as the need for low-cost hydroelectric power was paramount in the region. Development began in January 1930, and the dam, powerhouse, and first four operating units were turned over to Puget by Stone & Webster on February 1, 1933. Work on completion of the dam, powerhouse expansion and installation of six additional units by Chelan County PUD began in July 1951 and was completed on April 30, 1953. Construction of a second powerhouse, with its eight turbine generators located on the west bank of the river, began on August 4, 1974. The second powerhouse was placed in commercial operation on August 31, 1979. ==Electricity generation==