Scores waved tiny flags after taking the oath of US citizenship at the foot of the Statue of Liberty on Friday, 125 years after the iconic American symbol welcoming visitors and immigrants was dedicated.
"We are a nation of diverse people," secretary of the interior Ken Salazar said during the naturalisation ceremony on Liberty Island. "And that diversity strengthens our nation."
The new Americans, 125 immigrants from 46 countries, pledged to renounce foreign power, then posed for photos with their citizenship certificates.
The birthday party concluded with a 12-minute fireworks display choreographed to patriotic music.
"I feel like if you live in a place, you should have a say in the politics," said Paul Currie, who moved to the US from South Africa eight years ago. "Otherwise, you're an outsider."
Silvia Hodges, who came to the US from Germany in 1999, said the ceremony made her feel "like I belong here - and I really want to vote".
The Statue of Liberty, a gift from France, was conceived to symbolise the friendship between the two countries and a shared love of liberty. President Glover Cleveland dedicated the statue on October 28 1886.
New York mayor Michael Bloomberg said, "If anybody around this world wants to pick up their family and move so that their family can have freedom - freedom to speak, freedom to be in charge of their own destiny, all the freedoms that we have incorporated into the Bill of Rights - they always come to America."
Actress Sigourney Weaver recited Emma Lazarus' The New Colossus and gestured to the statue behind her at the words "a mighty woman with a torch".
The statue's interior will be closed for renovations for about a year, though Liberty Island will remain open.