CHICAGO Illinois Governor Pat Quinn is expected to sign same-sex marriage into law on Wednesday afternoon, which will make President Barack Obama's home state the 16th to allow such unions.
Illinois state senators voted to legalize gay marriage last February, and the state House followed suit by a slim margin earlier this month. Once signed by the Democratic governor, the law is due to take effect on June 1, 2014.
The Illinois measure is the latest in a series of recent victories for gay rights, coming after Hawaii's governor signed gay marriage into law last week and after New Jersey Governor Chris Christie dropped his legal opposition to such unions last month.
Illinois currently allows civil unions, which gay rights activists said does not go far enough.
But the proposal had been resisted by some African-American Democratic lawmakers who were under pressure from outspoken black Protestant churches to oppose it. The leadership of the Catholic Church in Illinois also opposed the proposal.
A Catholic bishop in Illinois, Thomas J. Paprocki of Springfield, said he was planning an exorcism ritual to protest the law at the same time as the governor's planned signing on Wednesday.
Opponents had expressed concern that under the proposed gay marriage law, religious organizations that declined to allow their facilities to be used for gay marriages could face lawsuits. The amended version of the bill provides safeguards for religious organizations.
A year ago, only six states - Massachusetts, Vermont, New Hampshire, New York, Connecticut and Iowa - plus the District of Columbia recognized same-sex marriage, but the number has since more than doubled.
Maine, Maryland and Washington became the first to extend marriage rights to same-sex couples by popular vote with passage of ballot initiatives last November. Gay marriage also became legal this year in California, Delaware, Minnesota and Rhode Island.
On the other side of the issue, voters in more than two dozen states have approved state constitutional provisions that define marriage as a union between a man and a woman, according to the National Conference of State Legislatures.
(Reporting by Mary Wisniewski; Editing by Sandra Maler)