The 1935 Dedication of Boulder Dam stamp is a 3 cent prepaid postage stamp. It was issued on September 30, 1935, to commemorate the dedication of the dam by President Franklin D. Roosevelt that same day. The stamp's first city was Boulder City, Nevada, which was a town that was fundamental in the dam's construction. There were over 73 million stamps printed.
Construction of the dam started in 1931 in Black Canyon of the Colorado River and lies on the Arizona/Nevada border. It is a concrete arch-gravity dam, which curves upstream and directs most of the pressure of the water to rock walls which then causes the force to compress the dam.
In 1936 building was completed and Lake Meade was impounded. The cost of the building the Boulder Dam was $49 million ($600 million today). 112 human casualties were reported being linked with the construction of the dam. In 1947 the U.S. Congress passed a joint resolution changing the name to Hoover Dam for President Herbert Hoover.
The Hoover Dam (as it has been called for some 73 years) contributes electricity generated for Nevada, Arizona, and California and attracts roughly a million tourists/visitors a year.