In American history, post-Reconstruction refers to something that happened after the Reconstruction (1863 - 1877). Particularly it may refer to:

The Nadir of American race relations

Disfranchisement after the Civil War

the post-Reconstruction era, the period right after Reconstruction, also known as Redemption

The return of Republicans to power in the South since the civil rights movement, especially during the Republican Revolution of the 1990s, (as in the phrase "first post-Reconstruction Republican...")