In times past, particularly the frontier days, it was common for states to consider a woman and man to be married if they lived together for a certain length of time, had sexual intercourse, and held themselves out as husband and wife, even though they never went through a marriage ceremony. Such a marriage was often called a common-law marriage.

Today, at least three-quarters of the states no longer recognize common-law marriages. The remaining states recognize common-law marriages, but with significant restrictions. In order for there to be a legal common-law marriage (in the states that recognize them), the couple must: have the capacity to marry; regard themselves as husband and wife; live together; and clearly represent themselves to others as being husband and wife. Merely living together is not enough to create a marriage.

If a common-law marriage is valid, the partners have the same rights and duties as if there had been a ceremonial marriage. An interesting problem occurs if a couple had a valid common-law marriage in a state that recognizes common-law marriages, but then moved to a state that does not recognize common-law marriages. Would the marriage still be valid? Under principles of conflict of laws, the answer usually would be "yes." Conflict of laws principles generally state that if a contract (in this case a marriage agreement) is valid in the place in which it was created, it will be treated as valid in a state to which the parties move, even though the parties could not have entered into a such an agreement in the new state.

A common-law marriage that is legal may end only with a formal divorce. There is not a United States counterpart to the tradition in Muslim law that allows a divorce to be accomplished by one party to the marriage–in Muslim law, that’s the husband–pronouncing the "Talek": "I divorce thee. I divorce thee. I divorce thee."

Sidebar:   Change of Name

A woman who marries may change her last name (also known as "surname") to that of her husband, but she is not required to do so. In the past, it was widely assumed that a woman would change her last name to her husband’s name when she married. Now society recognizes a woman’s right to take her husband’s name, keep her original name, or use both names. The general rule is that if a woman uses a certain name consistently and honestly, then that is her true name.