Six states and the nation's capital have recognized the legality of same-sex marriages, either by law or by court order.
But over the past decade and a half, each of the 30 states to consider constitutional amendments that would outlaw such unions has adopted the ban — from Alaska in 1998 to North Carolina earlier this year.
That may change on Election Day, when voters in Maryland, Washington, Maine and Minnesota — awash in money, messages and advertisements from both sides of the issue — will make their decision on whether to recognize gay marriage.