BOSTON — The St. Patrick’s Day parade in Boston will make history this Sunday as two gay and lesbian groups join the fun.

The advocacy group Boston Pride and OutVets, a group of gay military veterans, have been welcomed by the organizers.

“This is a tremendous leap forward,” Boston Pride organizer Sylvain Bruni said Friday.

Until now, gay rights groups have been barred by the South Boston Allied War Veterans Council from marching in the parade, which draws as many as a million spectators each year. Twenty years ago, the U.S. Supreme Court upheld the organizers’ right to keep gays out.

But Brian Mahoney commands the council now, and he’s shrugging off questions about sexual orientation.

Just like Pope Francis, he says, “Who am I to judge?”

This Sunday’s parade through the traditionally Irish-American enclave also will be shorter than years past: So much snow remains piled on sidewalks after the brutal winter that the city has had to cut the route in half.

And for the first time in two decades, a Boston mayor plans to be marching, too.

“With this year’s parade, Boston is putting years of controversy behind us,” Mayor Marty Walsh said Friday.

Boston’s mayors have boycotted the event since 1995, when the council took its fight to exclude gay groups all the way to the U.S. Supreme Court and won. The justices ruled unanimously that it would violate the First Amendment rights of private citizens who organize a parade if they are forced to include a group that doesn’t share its message.

“They’re not going to shove something down our face that’s not our traditional values,” said the council’s leader at the time, John “Wacko” Hurley, a year before the landmark 1995 ruling.

It would be eight more years before Massachusetts became the first state to legalize gay marriage, a trend that has since spread across most of the United States. Today, more than 70 percent of Americans live in states where gay marriage is allowed.

The council’s current leaders voted 5-4 in December to welcome OutVets as one of about 100 groups in this year’s parade. Boston Pride announced Friday that it also received an acceptance letter from the council this week.

“We’re excited to be there,” said Bryan Bishop, a 20-year U.S. Air Force veteran who founded the group representing lesbian, gay, bisexual and transgender veterans. “We’ve received nothing but positive feedback, from the mayor all the way down.”