Spectators await the start of the 2015 New York City...

Spectators await the start of the 2015 New York City Pride March on Sunday, June 28, 2015, in Manhattan. The parade starts uptown and ends near the Stone Wall Inn in Greenwich Village. Credit: CS Muncy

Under the rainbow clothing, glitter and giddy celebration, revelers at New York City's Pride March Sunday felt the full weight of the U.S. Supreme Court ruling that legalized same-sex marriage across the country.

Hundreds of thousands attended the march from midtown to the West Village, making for what officials said could have been the largest crowd in the event's more than four decade history. About 2 million lined the streets two years ago to celebrate same-sex marriage after it was made legal in New York State, said James Fallarino, NYC Pride media director.

This year's celebration started early -- with many arriving in the rain hours before the floats, elected officials and celebrities stepped off at noon.

"This is an extraordinary day in American history," Mayor Bill de Blasio said after the march through Manhattan. "This is a beautiful, beautiful celebration of the Supreme Court decision and of -- finally -- a huge step forward for equality in this country."

De Blasio, sporting a rainbow-striped tie and waving a rainbow flag, high-fived spectators along the route. He was joined by his wife, Chirlane McCray, and children, Chiara, 20, and Dante, 17.

Elaina Cuoco-Coton and Cherie Coton of West Islip said the Supreme Court decision gave this year's march special meaning. The couple was married at Bethpage State Park the first day same-sex marriage was legalized in New York.

Representatives of the city council, which has six members in its LGBT caucus, gathered at the march's starting line at 36th Street and Fifth Avenue before walking the route.

Two of Britain's most renowned film and theater actors served as grand marshals: Sir Derek Jacobi, who sprang to fame in the United States in "I, Claudius," and Sir Ian McKellen, best known for his roles in the "Lord of the Rings" and "X-Men" movies. Both are gay.

McKellen wore a rainbow sash and waved his rainbow-banded fedora at the crowd as he rode through the streets.

Sen. Charles Schumer (D-N.Y.) also participated. As he walked, he criticized states that were resisting issuing marriage licenses, saying they have to follow the new law "whether they like it or not."

The 300 or so floats were to be judged in the categories of best float, best performance, best dressed and most original. The original purpose of the march -- showcasing gay power and pride -- was remembered in two new award categories for best use of rainbow colors and best representation of the lesbian, gay, bisexual and transgender community.

Roots of the march date to 1969, when riots broke out at the Stonewall Inn in response to what was called police harassment. The riots lasted three days. On the anniversary in 1970, activists took to the streets without a permit in what is now considered the first Pride March.

In honor of that act of protest, the Pride March is still not called a parade.

What would become an annual event began as an attempt to transform how the country felt about gay people, at a time when coming out could jeopardize careers, friendships and families. Work remains to be done, many said.

Touro College law student Vanessa Cavallaro, 22, of Mount Sinai, said that despite the new freedom to marry, same-sex couples in many states face discrimination in housing, jobs and health care.

"I just hope supporters on social media will be there when we tackle these issues," said Cavallaro, who attended the march with her girlfriend, Nicole Vitale.

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