Eleven years after same-sex marriage was first made legal in Massachusetts, the U.S. Supreme Court ruled that the Constitution guarantees it throughout the country. The 5-4 decision rests in part on the court’s interpretation of the 14th Amendment, and states that limiting marriage only to heterosexual couples violates the amendment’s guarantee of equal protection under the law. Before the ruling, 36 states and the District of Columbia had legalized same-sex marriage. See a timeline highlighting changes in state policies from 1995-2015.