About 3 million people in New York City prepared to celebrate America's birthday, while hundreds of new citizens were sworn in at ceremonies around the country.
The festivities took place under heightened security after the attempted car bombings and airport attack in Britain over the weekend. In Washington, visitors were required to pass through 19 security checkpoints to reach the grassy central Mall.
"We're expecting a record crowd to come out this year and enjoy the fireworks," said U.S. Park Police spokesman Sgt. Robert Lachance. Past crowds there have reached 500,000 or more.
Security measures at the New York region's tunnels, bridges and airports remained heightened following the failed attacks on Glasgow and London last week, and no additional precautions were taken for the holiday, said Marc LaVorgna, a spokesman for the Port Authority of New York and New Jersey.
The country's birthday celebration opened in Philadelphia with a reading of the Declaration of Independence at Independence Hall, and descendants of signers of the original declaration were present for a symbolic ringing of the Liberty Bell.
About 1,000 people from around the world became U.S. citizens at Walt Disney World, raising their right hands in front of Cinderella's castle at the Magic Kingdom as the oath was read by Emilio Gonzalez, head of U.S. Citizenship and Immigration Services.
It was also a day to honor military service. The Army honored its one-millionth veteran at an American Legion post in Philadelphia.
The recognition went to Bronze Star recipient Bill Beck of Pennsylvania.
"I'd rather be honored with this than win a million dollars in a lottery, because my wife would spend a million in a couple of weeks and I'll have this for the rest of my lifetime," Beck said in a phone interview.
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