The Hoover Dam was built completed in 1935 and was considered was the greatest concrete project ever recorded, using more masonry than the Great Pyramid at Giza (4.5 million cubic yards) and equal to the amount needed to build a two-lane highway from Seattle to Miami, or a 4-foot-wide sidewalk around the Equator. It is the highest dam in the Western Hemisphere. The dam stands 726 feet above the Colorado River. It measures 1,244 feet across at the top, 660 feet thick at the base, and 45 feet thick at the top. It weighs a whopping 6.6 million tons, or at least the sum of its parts weighs that.
The Mike O’Callaghan–Pat Tillman Memorial Bridge came along 75 years later. It is an arch bridge that spans the Colorado River between the states of Arizona and Nevada. Located in the Lake Mead National Recreation Area approximately 30 miles southeast of Las Vegas, it was designed to reroute US 93 from its previous routing along the top of Hoover Dam and removed several hairpin turns and blind curves from the route. The new bridge, which opened in 2010, carries Interstate 11 and US Route 93 over the Colorado River. It was the most important part of the Hoover Dam Bypass project. It is jointly named for Mike O’Callaghan, Governor of Nevada from 1971 to 1979, and Pat Tillman, an American football player who left his career with the Arizona Cardinals to enlist in the United States Army and was killed in Afghanistan in 2004 by friendly fire.
While the original design of the Hoover Dam seemed like a great idea, it was shown to be dangerous as early as the 1960s. The dam was also inadequate for projected traffic volumes. Work on a different design began in 1998, and in March of 2001, the Federal Highway Administration selected the route, which crosses the Colorado River approximately 1,500 feet downstream of Hoover Dam. The construction of the bridge approaches began in 2003, and construction of the bridge itself began in February 2005. The bridge was completed in 2010 and the entire bypass route on October 16, 2010…opening to vehicle traffic on October 19, 2010. The Hoover Dam Bypass project was completed within budget at a cost of $240 million; the bridge portion cost $114 million. The bridge was also strategically placed to help prevent a terrorist attack, because it kept visitors away from the dam itself.