(June 17, 2008)--Some couples tied the knot after hours Monday night, but most county offices in California were closed at the exact minute gay marriage was legalized.

Tuesday is the day that hundreds, if not thousands, of gay couples will exchange vows.

The law banning gay marriage was officially voided at 5:01 p.m. Pacific time Monday, when most county offices were closed.

A UCLA study predicts that over the next three years, more than 100,000 gay couples from around the country could get married in California.

The law has residency requirement.

But it's also possible that a November referendum could overturn gay marriage again.

One of the first marriages was presided over by San Francisco Mayor Gavin Newsom, whose challenge to the state's marriage laws in 2004 led to the ruling by California's supreme court.

At City Hall, the Mayor helped marry a lesbian couple who are two pioneers of the gay rights movement.

They’re 87- and 84-years-old.

Opponents of gay marriage have not given up -- they're launching various legal challenges.

A hearing on one matter is scheduled for Tuesday.