Hoover Dam is named after Herbert Hoover, the Nation's 31st President. When construction of the dam was initiated, on September 30, 1930, Secretary of the Interior Ray Lyman Wilbur ordered that the dam be built in the Black Canyon of Colorado as part of the Boulder Canyon Project Act to be called Hoover Dam. By a Congressional Act of February 14, 1931, this name was made official. After Mr. Hoover left office, the names "Boulder Canyon Dam" and "Boulder Dam" were frequently used when referring to the dam, allegedly because the new Secretary of the Interior did not like Mr. Hoover. However, the name of the dam was never officially changed from "Hoover."

Source: US Bureau of Reclamation