CHICAGO » Gov. Pat Quinn, saying it was a "day of history," signed legislation yesterday legalizing civil unions for gay and lesbian couples, making Illinois one of about a dozen states that extend significant legal protections to same-sex couples.

About 1,000 people crowded into the Chicago Cultural Center to watch Quinn, a Democrat, sign the measure that supporters call a matter of basic fairness and opponents decry as a threat to the sanctity of traditional marriage.

"We believe in civil rights and we believe in civil unions," Quinn said before signing the bill to a roar of cheers and applause.

The law, which takes effect June 1, gives gay and lesbian couples official recognition from the state and many of the rights that accompany traditional marriage, including the power to decide medical treatment for an ailing partner and the right to inherit a partner’s property.

Five states already allow civil unions or their equivalent, according to the Human Rights Campaign. Five other states and Washington, D.C., let gay couples marry outright, as do some countries, including Canada, South Africa and the Netherlands. (Hawaii’s Legislature is considering a measure that passed last year but was vetoed by then-Gov. Linda Lingle.)

Illinois law will continue to limit marriage to one man and one woman, and civil unions still are not recognized by the federal government.

Opponents, including some religious and conservative groups, said the law is a step toward legalized same-sex marriage.

Some hope civil unions are a step toward full marriage for gay and lesbian couples, although sponsors of the civil-union bill have said they don’t plan to push for legalizing same-sex marriages, which have limited support in the Legislature.