Development: The U.S. Supreme Court has ruled that states cannot ban same-sex marriage, thereby requiring all states to issue marriage licenses to same-sex couples.
Background and History: State legislatures, voters and more recently the courts have made sweeping changes over the past two decades in laws defining whether marriage is limited to relationships between a man and a woman or is extended to same-sex couples. Before the U.S. Supreme Court ruling on Oct. 6, 2014, declining to hear cases on same-sex marriage, 31 states had either constitutional or statutory provisions that explicitly defined marriage as between a man and a woman and just 19 states and the District of Columbia allowed same-sex marriage. Now, at least 37 states and D.C. recognize same-sex marriage.