Now it has some big competition for that title just 1,500 feet downstream. Towering above the dam is a new bridge.
"I know that the Hoover Dam is one of the wonders of the world," U.S. Transportation Secretary Ray LaHood said at a dedication ceremony Thursday. "I don't know who gives that designation, but I hope the bridge will become another wonder of the world."
The new four-lane bridge -- 1,900-feet long, and perched 890 feet above the Colorado River -- is supposed to drastically cut travel time along the main route between Las Vegas and Phoenix.
Cars were previously routed more than six miles across Hoover Dam to cross the border, and had to stop at checkpoints.
The bridge was built at a cost of $240 million. It took more than seven years to build. But not only is it a marvel, it's also a memorial for two people hailed as local heroes..
The bridge, which officially opens next week, is named for former Nevada Gov. Mike O'Callaghan and Pat Tillman, the former NFL player who quit the Arizona Cardinals to join the Army Rangers and died in Afghanistan under friendly fire. Family members of O'Callaghan and Tillman watched the dedication ceremony from the span along with hundreds of construction workers and their families.
"I never had the honor of meeting Pat Tillman, but I share the nations admiration for him," said U.S. Senate Majority Leader Harry Reid of Nevada. "He was a humble man, a hero, who never wanted nothing more than to be seen and remembered as a regular guy."
With twin concrete arches measuring 1,060 feet, it's the longest bridge of its kind in the Western Hemisphere, according to the Transportation Department.
Officials say the bridge contains some 16 million pounds of steel, 30 cubic yards of concrete and 2 million feet of cable - enough to stretch well past Phoenix from Las Vegas.
The Associated Press contributed to this report.