Who came before Rosa Parks in protesting the segregation of public transportation?

The two women who refused to give up their seats on Montgomery, Alabama buses before Rosa Parks were Claudette Colvin and Mary Louise Smith. Colvin became pregnant in the months after her arrest and Smith's father was rumored to be alcoholic.

Predating those those Montgomery incidents were the cases of Irene Morgan, arrested in 1944 for refusing to give up a seat on a Greyhound bus in Virginia, and Sarah Mae Flemming, arrested in 1954 for sitting in a white person's seat on a local bus in Columbia, South Carolina. Flemming's case, which was heard twice in the Fourth Circuit Court of Appeals and dismissed without hearing by the Supreme Court in 1956, was used as a precedent in Parks' case.