His name was PBS Pinchback. It wasn't Douglas Wilder a Democrat elected governor of Virginia in 1990. He served as governor of Louisiana in the Reconstruction era (this period lasted about a decade after the Civil War). His term lasted from December 9, 1872 to January 13, 1873. A Republican Pinchback became governor his predecessor Governor Henry Clay Warmouth was impeached and removed from his governorship for political corruption.
Before becoming governor Mr. Pinchback was the only black officer in the Louisiana Native Guards during the Civil War. In 1868 he was elected to the Louisiana State Senate and after the death of the first black elected Lieutenant Governor of a US state, Oscar Dunn, he became Lt. Governor.
We may have a third if Ohio Secretary of State J. Kenneth Blackwell is successful in his race for governor and indeed we may have a fourth if Lynn Swann wins in Pennsylvania.