Oct. 10, 1972: Supreme Court dismisses Baker vs. Nelson, a Minnesota case filed by a gay couple seeking to marry, "for want of a substantial federal question."
Jan. 1, 1973: Maryland becomes the first state to pass a statute banning same-sex marriages.
May 5, 1993: Hawaii Supreme Court rules that denying marriage to same-sex couples violates the state Constitution.
Sept. 21, 1996: President Clinton signs the Defense of Marriage Act, denying federal benefits to married same-sex couples.
Nov. 3, 1998: Hawaii voters approve a constitutional amendment banning same-sex marriage.
Sept. 22, 1999: California is the first state to pass a domestic partnership law.
Nov. 18, 2003: Massachusetts Supreme Court legalizes same-sex marriage.
Nov. 2, 2004: Constitutional amendments denying same-sex marriage are passed in 11 states.
Nov. 7, 2006: Constitutional amendments banning gay marriage pass in seven more states.
Oct. 10, 2008: Connecticut Supreme Court legalizes same-sex marriage.
Nov. 4, 2008: California voters approve Proposition 8, which bans gays and lesbians from marrying.
April 3, 2009: Iowa Supreme Court legalizes same-sex marriage.
April 7, 2009: Vermont Legislature overrides veto, approves gay marriage.
May 6, 2009: Maine Gov. John Baldacci signs law legalizing gay marriage.
June 3, 2009: New Hampshire Gov. John Lynch signs law legalizing gay marriage.
Nov. 3, 2009: Maine voters overturn the state's gay marriage law at the ballot box.
Dec. 18, 2009: District of Columbia legalizes gay marriage.
Feb. 23, 2011: U.S. Attorney General Eric Holder says the Obama administration will no longer defend the Defense of Marriage Act.
June 24, 2011: New York legalizes same-sex marriage.
Feb. 13, 2012: Washington state legalizes gay marriage.
Feb. 16, 2012: New Jersey legislators approve same-sex marriage bill, later vetoed by Gov. Chris Christie.
May 9, 2012: President Obama becomes the first sitting president to announce his support for same-sex marriage.
Nov. 6, 2012: Voters approve constitutional amendments allowing gay marriage in Maine, Maryland and Washington state.
May 2013: Laws allowing same-sex marriage signed in Rhode Island, Delaware and Minnesota.
June 26, 2013: Supreme Court strikes down a key section of the Defense of Marriage Act.
Oct. 21, 2013: New Jersey Supreme Court legalizes gay marriage.
November 2013: Same-sex marriage legalized in Hawaii and Illinois.
Dec. 19, 2013: New Mexico Supreme Court legalizes gay marriage.
Oct. 6, 2014: Supreme Court refuses to hear state appeals from Utah, Oklahoma, Virginia, Indiana and Wisconsin.
Jan. 16, 2015: Supreme Court agrees to hear six consolidated cases from Kentucky, Michigan, Ohio and Tennessee.