This year, the revelry went beyond floats, music and dancing. It included wedding plans.
"We've been waiting to get married in Central Park for years, and now we got here just in time for history to be made," said Bryce Croft of Kettering, Ohio, who attended the parade with her partner, Stephanie Croft.
The two women are not yet legally married although they share the same name, and they are planning to move to New York and get married. They were in a restaurant when they learned that the same-sex marriage bill had passed.
"We cried over dinner, right into the mozzarella sticks," Stephanie Croft said.
Throngs of cheering supporters greeted Gov. Andrew Cuomo as he led off the parade two days after signing the historic bill that made New York the sixth state to extend full marriage rights to gay couples.
"New York has sent a message to the nation," Cuomo said before the march down Fifth Avenue. "It is time for marriage equality."
Revelers hoisted signs that said "Thank you, Gov. Cuomo" and "Promise kept."
Parade organizers said a half-million people participated.
Cuomo marched with his girlfriend, Food Network personality Sandra Lee, New York City Mayor Michael Bloomberg and openly gay elected officials including New York City Council Speaker Christine Quinn.
"You couldn't hear yourself think, it was so loud," Quinn said at the end of the parade route. "People were crying, jumping up and down and screaming. Everyone was smiling. It was unbelievable."
The crowd, standing a dozen people deep behind police barricades, whooped and screamed as hundreds of motorcycles roared down the avenue.
"I'm really, really proud of New York," said Hannah Thielmann, a student at Fordham University in the Bronx who attended with her girlfriend, Christine Careaga.
The couple, both 20, were dressed as brides.
Careaga said her mother called her crying tears of joy after the New York Senate voted on the measure Friday.
"Every mother wants her child to be happily married," Careaga said.
State Sen. Tom Duane, a Manhattan Democrat who is gay, said he and his partner had not decided when they would get married, "but now we get to decide, and it couldn't be better than that."
In Chicago, organizers of that city's parade scrambled to repair dozens of floats after someone slashed their tires overnight at a garage on the South Side.
Parade coordinator Richard Pfeiffer said as many as 50 of the approximately 75 floats had damaged tires. The parade was to go ahead as planned, though some of the 250 entries might be out of order.
"Whoever decided to do this is not going to affect the parade," Pfeiffer said. "We're all going to be out celebrating.
We're still going to go on."
Police spokesman Mike Sullivan said it was too early to determine if the damage was a hate crime.
In New York, the parade stepped off just after noon at 36th Street and Fifth Avenue and headed downtown. It ends at Greenwich and Christopher streets, near the site where gays rebelled against authorities and repressive laws outside the Stonewall Inn in Greenwich Village on June 28, 1969 - an event that gave rise to the gay rights movement.
A year later, several hundred people marched through the neighborhood to commemorate the riots in what is commonly considered the world's first gay pride parade.
This year's grand marshals include author and sex columnist Dan Savage and his husband, Terry Miller, who married in Canada; the Rev. Pat Bumgardner, senior pastor of Metroplitan Community Church of New York and a proponent of gay rights; and the Imperial Court of New York, which raises money for gay health and social services.
The law signed by Cuomo takes effect in 30 days. It was passed amid opposition from influential religious groups in the state.
Associated Press Writer Sophia Tareen in Chicago contributed to this report. AP Radio Correspondent Julie Walker contributed to this report.