"What do we want? Equality. When to we want it? Now," the protestors chanted.
The demonstrators were pushing Saturday to legalize same sex unions in Illinois.
"You have people shoving the Bible down your throat. 'Homosexuality is an abomination against God.' Fine, but you don't use that for making laws," said Maureen Brill, who participated in the protest.
The Freedom to Marry protest came as the California Supreme Court was preparing to revisit the controversial Proposition 8 measure that banned gay marriage.
"We know courts historically have responded to public pressure, and that's what we're aiming to do here today," the Gay Liberation Network's Andy Thayer said.
As a throng of couples waited inside the Cook County building to wed, several dozen supporters of gay marriage rallied outside with the intent of, once again, challenging the status quo.
Cook County Clerk David Orr, whose office issues marriage licenses, says he is a longtime supporter of gay marriage, but can't give marriage licenses to gay couples because of the law.
In a statement, Orr's office wrote in part, "Gay couples deserve to enjoy the same rights and legal protections as straight couples, whether it be getting married or making emergency health decisions, filing a joint tax return or receiving retirement benefits to which they are entitled."
John Robinson agrees. He and his partner were married in Massachusetts, where gay marriage is legal, and he wonders what's next for him since he moved to Illinois for a job.
"Legally, I'm in a quandary. I really would like to have my life simplified so I know that what we own together would pass along to him," he said.
But same sex marriage opponents say the issue is not just legal but also moral.
Ralph Rivera, a lobbyist for the Illinois Family Institute, which opposes gay marriage, said, "Don't believe that if this happens, that you have same-sex marriage with two men or two women, that polygamy doesn't have a legal basis, or a father and daughter doesn't have a legal basis. All the legality goes out the window."
And while some anti-gay marriage groups hope to get the issue on the ballot as a referendum in 2010, some Illinois lawmakers continue to review a gay marriage bill now pending in the newly formed Youth and Family Committee.
Cook County officials said there were no arrests as a result of Saturday's protest.