CHICAGO — Illinois Gov. Pat Quinn signed legislation Wednesday allowing same-sex weddings starting this summer, making President Barack Obama’s home state the 16th overall — and largest in the nation’s heartland — to legalize gay marriage.

“We understand in our state that part of our unfinished business is to help other states in the United States of America achieve marriage equality,” Quinn said before he signed the bill at the University of Illinois at Chicago on a desk once used by President Abraham Lincoln. He said part of that mission was to ensure that “love is not relegated to a second-class status to any citizen in our country.”

When the law takes effect June 1, same-sex couples can begin applying for marriage licenses.

Gay marriage is allowed in Washington D.C., and 15 other states; Hawaii’s governor signed a measure last week.