It comes up often here on AVVO - am I married under common law? Or, more often, do I need a divorce because I think I might be married under common law.
There are very few states that allow common law marriages. According to the National Conference of State Legislatures, currently, only 9 states (Alabama, Colorado, Kansas, Rhode Island, South Carolina, Iowa, Montana, Oklahoma, and Texas) and the District of Columbia recognize common-law marriages contracted within their borders. In addition, five states have "grandfathered" common law marriage (Georgia, Idaho, Ohio, Oklahoma and Pennsylvania) allowing those established before a certain date to be recognized. New Hampshire recognizes common law marriage only for purposes of probate, and Utah recognizes common law marriages only if they have been validated by a court or administrative order.
Here's a trap for the unwary. All states recognize the validity of common law marriages contracted in states in which the marriage was legal at the time it took place. So if you were married under common law but move to a state that doesn't allow common law marriages, you're still married - and if you want to leave that marriage you DO need a divorce.