SAN FRANCISCO -- San Francisco officially kicked off the annual gay pride celebration on Tuesday night with a ceremony at City Hall.

Mayor Gavin Newsom and some city officials raised the rainbow flag from the balcony of his city hall office, an annual tradition that officially starts the gay pride celebration.

A few hundred people joined the festivities, including a married couple from Finland. Marcos Kuusjarvi and Veli Eronan are spending two weeks in San Francisco. They are renting a house and along with other visitors providing a boost to the local economy..

At Pier 27, workers were busy creating the hundreds of floats and exhibits for Sunday's 39th annual parade.

This year, the Proposition 8 ban on same-sex marriage remains at the forefront for many gays and lesbians.

Organizers say numerous floats will reflect the community's continued struggle for the right to marry as part of their fight for equal rights.

The theme of this year's celebration is "In Order To Form a More Perfect Union."

Gay activists said the recent decision to count gay married couples in the 2010 census is long overdue. Many also said the community needs to continue to pressure President Obama to support gay rights -- something he promised to do during his campaign.

Lindsey Jones, the executive director of San Francisco Pride, said it falls to activists to continue to challenge what he called "crazy discriminatory" laws.

San Francisco Supervisor Bevan Dufty echoed those sentiments.

"We're never turning back and our issues have been on the front burner and I'm really proud that on a national level we're continuing to challenge any political institution," Dufty said.

This weekend's pride celebration is expected to draw one million people over two days.

Organizers say this weekend's festivities hold an added significance. The 40th anniversary of the Stonewall riots in New York, which mark the beginning of the gay rights movement, falls on Sunday -- the same day of this year's San Francisco pride parade and celebration.