 With most work finished on the dam itself ( the powerhouse remained uncompleted ) , a formal dedication ceremony was arranged for September 30 , 1935 , to coincide with a western tour being made by President Franklin D. Roosevelt . The morning of the dedication , it was moved forward three hours from 2 p.m. Pacific time to 11 a.m. ; this was done because Secretary of the Interior Harold L. Ickes had reserved a radio slot for the President for 2 p.m. but officials did not realize until the day of the ceremony that the slot was for 2 p.m. Eastern Time . Despite the change in the ceremony time , and temperatures of 102 ° F ( 39 ° C ) , 10 @,@ 000 people were present for the President 's speech in which he avoided mentioning the name of former President Hoover , who was not invited to the ceremony . To mark the occasion , a three @-@ cent stamp was issued by the United States Post Office Department — bearing the name " Boulder Dam " , the official name of the dam between 1933 and 1947 . After the ceremony , Roosevelt made the first visit by any American president to Las Vegas . 
