Southern colonies outlawed interracial marriage in the 1690's. Wyoming was the last state to prohibit it, in 1913. It joined 41 other states, every state where the black population reached 5 percent.
Though some states had repealed their anti-miscegenation laws before the Civil War, 16 still had them by the time the US Supreme Court declared them unconstitutional in 1967. (info from The New York Times; photo of O. J. Simpson and wife/alleged murder victim Nicole Brown Simpson from judiciaryreport.com)