From the Chicago Sun-Times:

Gov. Quinn will enact legislation that will allow same-sex couples to enter into civil unions during a bill-signing ceremony Monday that could go down as one of the largest in state history.

The governor's office has been publicizing the bill-signing for a week and expects as many as 1,000 people to show up at the ceremony, which will be held at the Chicago Cultural Center, 78 E. Washington St.

The civil unions law will take effect on June 1st.