Sept. 30, 1935: Hoover Dam dedicated

Although the Hoover Dam is now named for Herbert Hoover, who was president when the project started, it was President Franklin D. Roosevelt who dedicated the dam in 1935 as part of a longer tour of the Western U.S. (The dam wasn’t fully completed until the spring of 1936, an impressive two years ahead of schedule.) Like many dams, it was built to store water and create electric power for the growing communities of the Southwest, especially Nevada, Arizona and Southern California.

One of the most difficult building projects of the modern era — more than 100 workers lost their lives during its construction — it was at the time the largest concrete structure ever built. The dam contains 3,250,000 cubic yards’ worth of concrete, hauled in by giant bucket — enough to pave a two-lane highway from San Francisco to New York.

About a million people visit the dam every year, many of them making the 30-mile drive east from Las Vegas. Although tours were halted after Sept. 11, 2001, modified tours (restricting access to the dam’s interior, where visitors had once been allowed) later resumed. While it’s easy to reach the dam on your own, some visitors prefer to let one of the area’s many tour guides show them around by bus or even helicopter.

Before 2010, Highway 93 went right over the top of the dam, making for an exciting crossing from one side of the Colorado River canyon to the other. In 2010, the Hoover Dam Bypass bridge — a span that is itself an engineering feat — was completed, meaning those traveling by car get a side view instead of a top-down view of the dam’s giant white face.