The Statue of Liberty has been opened to the public for the first time since the 11 September 2001 attacks.
The statue is now open to the public for the first time in three years
The ceremony took place amid a heightened terror alert, but New York Mayor Michael Bloomberg said it was right not to postpone it.
"To stay home and lock our doors is what the terrorists want", he said, and Americans would not be "coerced".
Millions of dollars of donations have been raised to install a state-of-the-art security system for the landmark.
After a rendition of the national anthem from a military band, site superintendent Cynthia Garrett told the crowd the island was "a place for contemplation and remembrance, inspiration and renewal".
"This [place] is one of the most magnificent and recognisable in America and in the world. An enduring symbol of freedom, the Statue of Liberty represents America's past, present and future," she said, her voice beginning to break.
But visitors to the island will now have to undergo much tougher security screening before being allowed close to one of the US' most famous landmarks.
They will be screened once before they board ferries to Liberty Island and again when they enter the 305-foot (93m) statue.
The second screening is said to include a device which blows air through clothes as it tests for the presence of explosives particles.
The opening ceremony was held amid higher security alerts prompted by apparent intelligence of possible planned al-Qaeda attacks on major US financial institutions - including the New York Stock Exchange and the Citigroup building in Manhattan.
Police snipers monitored Tuesday's proceedings.
Authorities have decided to keep the crown of the statue closed to visitors, citing public safety concerns - though that decision has attracted some criticism.
Mr Bloomberg insisted a new observation deck on the statue's pedestal, some 45m up, compensated for that by offering new views of the statue and New York Harbor, but not all visitors on Tuesday were convinced.
"It's disappointing, but I can understand it," said Brenda
Pickett from Kansas, one of thousands of tourists who crowded onto the first two boats leaving Manhattan for the short trip to the island.
"Things are starting to go forward, even if we are remembering the past," she said of the reopening, according to AFP news agency.
Tom Mom, from the Netherlands, said the significance of the statue was felt beyond the shores of the US.
"It's a good sign for the world... because it symbolises freedom, and that's also an important value for the rest of the world," he said.
New attractions on Liberty Island will also include introductory guides to the statue using laser lights to pick out certain features.
"I hope every child in America and every child around the world gets to see this statue," Mr Bloomberg said.
France gave the statue to the US in 1886 as a symbol of the friendship that started during the American Revolution.