 "Boulder Dam" is actually Hoover Dam. Congress authorized the  Boulder Canyon Dam Project in 1931 and, it being traditional to name  big federal dam projects after the sitting President, named it  Hoover Dam. Franklin Roosevelt defeated Hoover in 1932 but could not  officially change the name set by Congress. Harold Ickes (FDRs  Interior Secretary) however issued a memo directing that his  employees "...will refer to the dam as Boulder Dam in this  pamphlet as well as in correspondence and other references...." In  1947, after Roosevelt and Ickes had died, Congress passed a  resolution to "restore" the name of Hoover Dam. But until that time,  all official, tourist and other promotional materials called it  "Boulder Dam." The publics recognition with the old name was still  apparent in the movie (released in 1950) through the script and the  highway signage seen enroute.