Colorado Governor John Hickenlooper on Thursday signed a civil unions bill into law.

Hickenlooper, a Democrat, signed Senate Bill 11 at the Colorado History Center near the Capitol.

Hundreds looked on chanting “Equal! Equal!” as Hickenlooper made history.

“There is no excuse that people shouldn't have all the same rights,” Hickenlooper told the cheering crowd.

The measure cleared the House last week on its third attempt. Republican House leaders last year refused to allow the bill to come up for a vote.

The drama of the previous two sessions was in sharp contrast to the ease with which the bill sailed through the General Assembly this year now that Democrats have regained control.

Gay rights advocates say passage is telling because voters in the state have twice backed laws hostile to gays. In 1992, voters approved of banning municipalities from enacting anti-discrimination laws based on sexual orientation. Known as Amendment 2, the Supreme Court declared it unconstitutional four years later. A constitutional amendment defining marriage as a heterosexual union was approved by voters in 2006.

The civil unions law takes effect on May 1.

Colorado joins five states – Illinois, Delaware, Hawaii, New Jersey and Rhode Island – in offering the union. Nine states plus the District of Columbia allow gay couples to marry.