Philadelphia celebrated its place in history as the birthplace of the country Saturday with patriotic revelry that was a little less rough around the edges than in recent years.

There was no stampede down the Benjamin Franklin Parkway, like the 2013 panic at the crescendo of a fireworks show. And the acts on stage for the Philly 4th of July Jam did not send 6ABC scrambling to cut expletives from the live television broadcast.

In all - and even with a lingering but ill-defined warning of a potential uptick in terrorism threats - the Fourth of July was a happy and mellow affair in the city where it all started.

A spate of rain showers did little to dampen the patriotic fervor on the Parkway.

The celebration was capped by a massive open-air concert, headlined by hometown favorites the Roots along with R&B singer Miguel, country singer-songwriter Jennifer Nettles, and other acts, before a grand-finale fireworks show.

The Roots had promised a special guest, and didn't disappoint as CeeLo Green appeared to sing the Gnarls Barkley hit "Crazy."

City officials had expected more than 700,000 people to attend a day of events on the Parkway from noon until 11 p.m.

By the time the Roots took the stage, city officials estimated the crowd to be at least 175,000 and growing, as people continued flowing in to watch the fireworks.

The fireworks display was delayed as the music went long. It started around 11:20 and caused backups on Interstate 676 as drivers slowed to watch.

Michael Resnick, the city's director of public safety, said some cars were even "backing up and driving the wrong way on 676 to get back to 95."

Enthusiasm for the performers, the national holiday, and Philadelphia were clear.

Mayor Nutter, in his last Fourth as the city's official cheerleader, roused the crowd with excitement for what Philadelphia does best:

"We're a big city that does big events well!" Nutter shouted from the main stage, touting the upcoming visit to Philadelphia by Pope Francis and the Democratic National Convention, which will take place here in July 2016.

Some complained of long lines for the toilets - Antonio Vicar, 25, waited 45 minutes with his 3-year-old Jahaiva.

The high notes of the evening - literally and figuratively - came from Miguel, a sultry singer who was a hit with the ladies.

"I like Miguel," said Kiara Taylor, a 25-year-old Paulsboro native swaying with her 4-year-old son Kahlil. "His music, and he's cute."

"That's her man," said her best friend, Bonita Collins.

David Mitchell, 39, came to the concert dressed as Uncle Sam.

Mitchell and his fiancée, Amanda Venkatesan, 35, live in Riverhead, N.Y., but came to Philadelphia to celebrate the Fourth because it's an "American, patriotic city," Mitchell said.

The concert, with a sizable police presence, was largely peaceful and uneventful. One officer injured her wrist when she fell from her bicycle while on patrol.

The Department of Homeland Security and the FBI last week warned law enforcement agencies of a potential increased risk of terrorism during the national holiday.

City officials said there were no specific threats to Philadelphia.

Officers mingled, returning high-fives and light banter from festival-goers. One officer called a young woman over from her small group of friends. What, he wanted to know, was that small metal pole?

It was that 2015 symbol of all things young and summer: the selfie stick.

She gave him a demonstration, showing off the button on the bottom that takes the photo. Then she snapped a selfie.

Saturday's concert was preceded by the Party on the Parkway, featuring games, live music and the chance to mingle with athletes planning to compete for the U.S. in the 2016 Olympic Games in Rio de Janeiro.

Friends Jane Sheil and Jenny Gray stood in line on the Parkway to take a photograph with Jordan Burroughs, an American wrestler who won a gold medal in London.

Gray, 36, now lives in Royersford, but was living in London in 2012. Sheil, 41 of Center City, came to visit and the two watched Olympic canoeing together.

"We're trying to get to Rio in '16!" Gray said Saturday as they snapped a picture with Burroughs.

Waiting for the concert to start, Diane King, 50, of Mickleton, N.J., joked that New York had stolen all the best musicians, who should be performing in America's true birthplace.

"This is where it all began," she said. "This is the birth of our nation."

Attendees found many ways to the pass the time before the concert - breakdancing, jump-roping, kissing strangers.

Kendall Currier, a 21-year-old Drexel film student, decided to use the holiday festivities to raise money for a science-fiction film she is making.

Around her neck was a square cardboard sign: "Kissin' booth. $1.00 per smooch."

"I've gotten several kisses," said the Houston native. "Maybe 15. Guys and girls. . . . Not to brag, but I'm a pretty good kisser."

Amit Patel, 31, of Bensalem, agreed. "That was pretty good," he said.

The Fourth of July festivities began Saturday morning at the historic landmark where the country began 239 years ago, at Independence Hall, with a ceremony commemorating the adoption of the Declaration of Independence.

The history did not stop there.

At Independence Hall, revelers also commemorated the 50th anniversaries of the first major LGBT protest in the country and the Voting Rights Act, and the 150th anniversary of the 13th Amendment to the U.S. Constitution, which abolished slavery.

That event was capped by a 1.2-mile Independence Day Parade through Old City to the Delaware River. Some 6,000 marchers from around the country were said to attend.

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@ByChrisBrennan

Inquirer staff writers Jonathan Lai, Erin McCarthy, Caroline Simon, Cat Coyle, and Madeline R. Conway contributed to this article.