The party will continue at Civic Center, with live music, speakers, food and drinks. All ages are welcome. The event is free.

The Pride Parade caps a month of gay-themed festivities and is expected to draw its regular cast of colorful characters and city leaders, gawkers and cheering spectators. There will be some 200 floats and hundreds of thousands of people lining Market Street.

But this party will also have a clear political message, coming in the wake of the state Supreme Court's ruling upholding the voter-approved ban on same-sex marriage. The theme for this year's parade is: "To Form a More Perfect Union."

"We're working on two things: legalizing same-sex marriage and making the country a better place," said Mikayla Connell, president of San Francisco Pride's board of directors. "The theme touches upon the inherent promise of life, liberty and equality for all."

The parade will be led off by Dykes on Bikes, a group of lesbians on motorcycles. Some of the new additions to this year's parade include: Army National Guard Lt. Dan Choi, a gay Arabic-speaking linguist who was dismissed after coming out on national television.

Choi will march with a new organization called Knights Out, which supports gay and lesbian military members. And, to mark the 40th anniversary of the Stonewall riots in New York's Greenwich Village, seen as the beginning of the modern gay-rights movement, a contingent of Stonewall veterans is expected to march.

Started as a way to protest discrimination against homosexuals, gay-pride events are now held in dozens of cities around the globe.

"We've come a long way since these events started, but we have a long way to go," Connell said. "We're still out in the streets. We're still fighting for equality."

For information on the events leading up to the parade, including the Dyke March and party at Dolores Park on June 27, go to www.sfpride.org.{sbox}

E-mail Julian Guthrie at jguthrie@sfchronicle.com.

This article appeared on page R - 20 of the San Francisco Chronicle