What happened at southern democrats gained power?

When southern Democrats gained power, they put an end to Reconstruction.

Explanation:

The end of Reconstruction was a staggered process, and the period of republican control ended at different times in different states. With the Compromise of 1877, military intervention in Southern politics ceased and Republican control collapsed in the last three state governments in the South. This was followed by a period that white southerners called "Redemption," during which state legislatures dominated by whites enacted the Jim Crow laws and, beginning in 1890, deprived the majority of African Americans and many poor whites of a combination of constitutional amendments and electoral laws. The white memory of the Reconstruction of the Southern Democrats played an important role in the imposition of the system of white supremacy of segregation, of second-class citizenship for African-Americans using the laws known as Jim Crow laws.