Aaron Weisinger, 26, got down on one knee on the crown's small floor, pulled out a diamond ring and proposed to his girlfriend, Erica Breder. Stunned, she whispered an immediate yes.
"To propose in the crown was perfect," the 25-year-old Breder said later.
Cheering the Walnut Creek, Calif., couple, fellow visitors also felt the gravity of the occasion.
"I feel the Statue of Liberty represents global unity, a sign that our world must unify," said Barbara McLean, 57, of Atlanta. After ascending the total of 354 steps to the statue's crown, she sang "America the Beautiful" to applause from her fellow visitors.
"I think it represents a beacon of hope that, even in difficult times, that dreams can be made," she said.
The statue was closed to the public after the Sept. 11, 2001, attacks. The base, pedestal and outdoor observation deck were reopened in 2004, but the crown remained off-limits.
The National Park Service says the crown remained closed because the narrow, double-helix staircases could not be safely evacuated in an emergency and didn't comply with fire and building codes.
Tourists often suffered heat exhaustion, shortness of breath, panic attacks, claustrophobia and fear of heights, spokesman Darren Boch said.
New handrails have since been installed to help with the climb, and only 30 people per hour are allowed up the dark, small staircase. They are guided by park rangers along the way.
The first 30 huffed and sweated as they made their way up stairs sometimes too small to fit an entire foot, but most later said the climb wasn't as bad as they had anticipated.
Weisinger was drenched in sweat as he reached the top, but not just because of the workout. He had planned for months to propose in a place full of personal significance -- his grandparents, immigrants from Eastern Europe, arrived at nearby Ellis Island.
"I was nervous on the way up, but I was trying to hide it by saying it was the hike up," he said later. He and Breder, who have been together for three years, both teared up after his proposal.
Rep. Anthony Weiner, D-N.Y., pushed for years for the crown to be reopened, once calling the decision to close it off "a partial victory for terrorists."
The reopening "represents some personal vindication," he said Saturday.
"It's nice to pat Lady Liberty's toes. It's nice to stand and breathe the air on Liberty Island, but you really haven't lived the experience until you've gone up to the crown," he said. "A lot of Americans are able to see that now." Some of the crown's 25 windows offer a view of the Manhattan skyline, no longer punctuated by the 110-story twin towers of the World Trade Center.
So far, about 14,500 tickets to the crown have been sold, most of them for visits through the end of August. Tickets currently on sale are for visits in the fall and beyond. Tickets for the July Fourth weekend sold out within hours.
"I feel like I was just born today," said Andrea Balfour, 38, as she prepared to go up to the crown with her daughter, Mona. Mona won an essay contest to get to go up to crown Saturday -- her 13th birthday.
The visit was the Staten Island pair's "biggest dream," Balfour said.
Marking the historic date, seven members of the U.S. armed forces were sworn in as citizens Saturday at the statue's base. "It's the very diversity of this country that has made us strong," Secretary of the Interior Ken Salazar said.
The statue, 305 feet tall to the tip of its raised torch, was designed to mark the 1876 centennial of the Declaration of Independence. It faces the entrance to New York Harbor, welcoming the "huddled masses yearning to breathe free," in the words of Emma Lazarus, engraved on a bronze plaque inside the statue.
The torch has been closed since it was damaged by a saboteur's bomb in 1916.
Visitors are now screened before boarding ferries and again before they can visit the museum in the base or climb to the top of the pedestal.
Jennifer Stewart won a Statue of Liberty lookalike contest to join the first group of visitors headed to the crown. The Brooklyn Heights resident, who has imitated the statue for 23 years, arrived in full costume and green makeup.
"Being able to perceive the world through her eyes, from Liberty's crown -- I just feel it's so important to maintain the opportunity to literally be a part of liberty," she said.