On Nov. 18, 2003, Massachusetts became the first state to legalize same-sex marriage following a ruling by the state's highest court. In the five years since the Massachusetts decision, 26 states have amended their constitutions to ban gay marriage. Before the Massachusetts ruling, only three states had passed constitutional amendments prohibiting the practice - Alaska in 1998, Nebraska in 2000 and Nevada in 2002. In 1998, voters in Hawaii had approved an amendment granting the state legislature power to determine state policy on same-sex marriage, but the amendment itself did not ban gay marriage.
The only state to ever reject a constitutional ban on gay marriage was Arizona, in 2006. But in the most recent election, on Nov. 4, 2008, Arizona voters reversed course and approved an amendment banning same-sex marriage. On the same day, voters in California and Florida also approved similar amendments.
In addition to these constitutional amendments, legislatures in 42 states have passed laws limiting the legal definition of marriage to a union between a man and a woman. But a few of these restrictions were overturned by state courts, prompting many same-sex marriage opponents to argue that the practice can only effectively be banned by state constitutional amendments.