"black person," 1838, American English, originally the name of a black minstrel character in a popular song-and-dance act by T.D. Rice (1808-1860) that debuted 1828 and attained national popularity by 1832:
Where and how Rice got it, or wrote it, is a mystery. Even before that, crow (n.) had been a derogatory term for a black man. Association with segregation dates from 1842, in reference to a railroad car for blacks. Modern use as a type of racial discrimination is from 1943. In mid-19c., Jim Crow also could be a reference to someone's change of (political) principles (from the "jump" in the song).