With the stroke of the governor's pen, Illinois later Wednesday will become the 16th state in the nation to allow same sex couples to marry.
A packed house is expected to be on hand to witness Gov. Pat Quinn will sign the legislation -- SB10 -- at 3:30 p.m. at the University of Illinois at Chicago Forum. The Chicago Sun-Times' Michael Sneed reported Quinn will sign the bill on the desk Abraham Lincoln used to write his first inaugural address.
At about the same time advocates are celebrating, Bishop Thomas Paprocki will offer "Prayers of Supplication and Exorcism in Reparation for the Sin of Same-Sex Marriage" at the Cathedral of the Immaculate Conception in Springfield.
The Illinois Senate on Nov. 5 followed a long-awaited House vote to approve gay marriage. The bill passed the House 61-54, obtaining the 60 votes needed for passage. The Senate passed it an hour later.
"At the end of the day, all we're talking about is treating every family in the state of Illinois with the same equality and justice under the law as others," bill sponsor Rep. Greg Harris said.
Just 14 states and the District of Columbia allowed for same sex marriage when both houses of the Illinois General Assembly approved the measure. Hawaii Gov. Neil Abercrombie signed legislation just last week, making that state number 15.
Illinois' law takes effect June 1, 2014 and is expected to increase business and tourism spending in the state. A 2013 study by UCLA's The Williams Institute said that allowing same-sex couples to marry in Illinois would generate up to $103 million in new spending in the first three years. The Illinois Office of Tourism has already beefed up its website to promote gay-friendly spots in Illinois.
Cook County Clerk David Orr said his offices will be open on June 1, a Sunday, so gay couples can get their marriage licenses. In central Illinois, Champaign County Clerk Gordy Hulten said his office will be open, and in southwestern Illinois, Madison County Clerk Debra Ming-Mendoza said the office will open to issue marriage licenses June 2.
Quinn signed civil union legislation into law in 2011. Since then, the governor's office said more than 6,000 Illinois couples have joined in a civil union. The bulk of them have been in Cook County.
The Associated Press contributed to this report.