Edith Windsor, a gay rights activist whose case before the U.S Supreme Court paved the way for legalization of same-sex marriage, died Tuesday at 88.

Windsor's wife, Judith Kasen-Windsor, confirmed her death, according to reports. The couple started dating in 2015 and married last year.

Windsor served as the lead plaintiff in the Supreme Court case challenging the constitutionality of the Defense of Marriage Act, the 1996 law prohibiting same-sex couples from being recognized as spouses by the federal government and denying same-sex couples federal benefits available to married heterosexual couples.

The Supreme Court struck down part of the Defense of Marriage Act in 2013 but left in place laws in 37 states banning gay marriage. In 2015, the high court legalized gay marriage nationwide.

Windsor brought her case challenging the Defense of Marriage Act after marrying Thea Spyer, a psychologist, in Canada in 2007. The two had been engaged for 40 years.

Spyer died in 2009, and after inheriting her estate, Windsor was subject to a tax bill of $363,053, since, under federal law, she could not receive a spousal exemption from the estate tax.

She later sued and said the Defense of Marriage Act was unconstitutional because it singled out married same-sex couples.

Windsor was born in Philadelphia in 1929 and graduated with a bachelor's degree from Temple University in 1950, according to the New York Times. She received a master's degree in applied mathematics from New York University in 1957 and worked as a computer programmer with IBM.