Thirty visitors, many from other countries, were the first Saturday to climb the 354 steps to the crown, U.S. Interior Secretary Ken Salazar said.
"Once again, Americans can climb to Lady Liberty's crown and gaze out over New York harbor, where so many of our ancestors first saw the New World," Salazar said at the reopening ceremony.
The National Park Service cited safety and security reasons when it closed the crown in 2001 after terrorists destroyed the nearby World Trade Center.
Saturday, Aaron Weisinger, 26, of New York, climbed to the crown and proposed marriage to his girlfriend, Erica Breder, 25, the New York Post reported. She accepted.
"It's a pretty unique spot," Weisinger said. "It is the Fourth of July. It's special to us, it means independence, it means freedom. To do it in the crown was even more special."
The 305-foot monument of a robed woman holding a torch was presented by France to the United States in 1886 to celebrate its centennial.