Activists in California celebrated Harvey Milk Day knocking on doors to build support for gay marriage.

Saturday was the inaugural day honoring the slain gay rights leader.

Sharon Osbourne and daughter Kelly opened their Hidden Hills home to host a fundraiser sponsored by the state's largest gay rights advocate, Equality California.

On Friday, speaking to a crowd at San Francisco's LGBT Community Center in the Castro District, House Speaker Nancy Pelosi, a Democrat, said Harvey Milk helped open doors for the gay community.

"We'll come right back to Harvey Milk when he said his victory signaled a green light to all who were disenfranchised," Pelosi said. "A green light to move forward and that the doors are open to everyone."

California lawmakers have designated May 22 - Milk's birthday - as Harvey Milk Day.  Milk would have turned 80 this year.

On Saturday, activists returned to the roots of Milk's legacy by canvassing neighborhoods where voters had helped approve Proposition 8, the 2008 initiative that trumped a California Supreme Court ruling in favor of gay marriage. Groups opposed to the gay marriage ban say they'll attempt to roll it back in 2012.

Milk scribe Dustin Lance Black explained to gay website gay . com why the event was important: "You see Harvey doing that in the documentary The Times of Harvey Milk. In the Bay Area he used to go into neighborhoods that were not favorable to equality, and [in the film] you can watch the faces of the people who are meeting gay and lesbian people for the first time. I think a lot of them were horrified, but it creates change. We're hoping to have that same reaction."

In Los Angeles, volunteers gathered at the East Los Angeles Service Center, where they heard from Black and several local politicians, including Los Angeles City Councilman Jose Huizar and state Assemblyman Hector De La Torre, a Democrat from South Gate.

They fanned out across the city to knock on doors in East Los Angeles, Maywood, Commerce, Huntington Park, South Gate and Montebello, the Los Angeles Times reported.

"We become human when we tell our stories," Marc Solomon, marriage director of Equality California, told the paper.

"Harvey Milk was an activist, a fighter and believed so strongly in personal stories as a way to make progress happen," he added. "So it's very befitting to do that."

At least 25 cities throughout the nation joined in celebrating the memory of Harvey Milk.

Governor Arnold Schwarzenegger reluctantly signed into law state Senator Mark Leno's Harvey Milk Day bill last October. Schwarzenegger rejected a similar measure the previous year. In vetoing the first bill, Schwarzenegger said Milk's accomplishments should be celebrated at the local level.

Milk's 1977 election to the San Francisco Board of Supervisors made him the first openly gay elected official from a major U.S. city. The next year, Dan White, a disgruntled former supervisor, gunned down Milk and San Francisco Mayor George Moscone inside City Hall. During Milk's short tenure, the camera shop owner turned politician dramatically increased the visibility of the burgeoning gay rights movement.