“When did the state not define legal marriage in America?”
It always has and American law has roots in Christendom. American law derives from British common law. British common law goes back at least to the Doom Book of Alfred the Great circa AD 893. The Doom Book itself was compiled from the legal codes of the three Christian Saxon kingdoms of Wessex, Kent and Mercia.
But in that time there were also ecclesiastical courts, so not everything was handled by the State: this is the root of the disagreement between myself and Ansel12 — I do not believe that the government should be involved in defining marriage, he does; I do not believe that making a law
will solve the problem, he does; I believe the best way to remedy this is for Christians to act like marriage is sacred (something disproved, in general, by divorce-rate statistics [and accepting divorce for any-old-reason]) and Ansel [apparently] does not.