Crowds braved rain to mark the Fourth of July holiday, cheering as the city’s massive fireworks display lit up the sky and for the first time seemed to set the East River’s surface aflame.

People sporting ponchos and umbrellas stood along the East River to see the Jellyfish, which resembles the underwater creature, and the Electric Rice Krispies, crackling metallic shells.

For the first time, the annual Macy’s show featured exploding shells aimed down, not up. The shells exploded on the surface of the East River, remain illuminated for a few seconds and then fade.

“Awesome!” exclaimed Ben Fedak, a Queens musician taking in the show with his brother, before dazzling green shells exploded above him. “This is the best fireworks show that I’ve ever seen.”

The 30-minute show was billed as the nation’s biggest, with 40,000 fireworks. Eight barges on the East River and at the South Street Seaport set off an average of 1,300 shells per minute.

The program featured musical performers as part of the nationally televised broadcast, including Martina McBride, Joss Stone and “American Idol” winner Jordin Sparks.

Organizers estimated about 3 million people withstood the sogginess to turn out, about the same number as the year before, while another 8 million watched on television. The organizers had called their fireworks show “waterproof.” Police do not give crowd estimates.

In Philadelphia, the celebrations included a reading of the Declaration of Independence at Independence Hall, and descendants of those who signed the original document were on hand for a symbolic ringing of the Liberty Bell. Storms did not stop the fireworks show.

The threat of storms, however, forced officials in several eastern Pennsylvania cities to postpone fireworks shows. And dry weather curtailed some celebrations, including Breckenridge, Colo., where there was a high fire danger.

The festivities and patriotic observances took place under heightened security in the aftermath of the attempted car bombings in Britain.

Hundreds of officers from about 20 law enforcement agencies were on duty in Washington. The Mall was fenced off and visitors were required to pass through 19 security checkpoints, which opened at 10 a.m.

Severe weather brought a tornado warning to Washington’s suburbs, prompting authorities to evacuate the thousands of people gathered at the National Mall for holiday festivities. It reopened hours later.

Two fireworks crew members were injured when at least two unexploded shells went off on the ground. One had severe but non-life threatening burns, and the other was treated at the scene, authorities said.

Security measures at the New York region’s tunnels, bridges and airports remained heightened following failed attacks on Glasgow and London last week, and no additional precautions beyond those already in place were taken for the holiday, said Marc LaVorgna, a spokesman for the Port Authority of New York and New Jersey.

In Massachusetts, 20 local, state and federal agencies were assigned to help police the annual Boston Pops concert and fireworks show. Car and boat traffic were banned from the area and security was tightened at mass transit stations.

About 1,000 people from around the globe 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.

“I dreamed for this moment for 13 years, and finally this is my last dream that I have,” said Marta Hima, who came from Colombia and now lives in Davenport, Fla.

More than 350 new citizens were sworn in at Phoenix. “Now I feel like I can be part of this community,” said Alicia Gray of Gilbert, Ariz., who came to the United States from Mexico in 1996 and brought her American husband, her children and in-laws. “I’m more a part of this country now.”

It was also a day to honor military service. The Army honored its millionth veteran at an American Legion post in Philadelphia.

The recognition went to Bronze Star recipient Bill Beck of Steelton, Pa.

“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.