Final answer:
The removal of federal troops in 1877 in the South brought about rapid legal discrimination against blacks.
Step-by-step explanation:
The event that occurred in 1877 in the South that brought about rapid legal discrimination against blacks was the removal of federal troops
After the Civil War, federal troops were stationed in the South to enforce civil rights laws and protect the rights of newly freed African Americans. However, in 1877, as part of a compromise to resolve the disputed presidential election, federal troops were withdrawn from the South. This withdrawal allowed Southern states to enact and enforce discriminatory laws known as Jim Crow laws, which promoted racial segregation and denied African Americans their civil rights.