The laws enacted immediately after the Civil War that were designed to maintain the social structure of slavery were the Black Codes. These laws were passed in Southern states in 1865 and 1866 to restrict the freedoms of African Americans and ensure their availability as a cheap labor force, effectively attempting to maintain the social and economic hierarchies that slavery had established.
The other options mentioned have different contexts:
- Compromise of 1877 was an agreement that resulted in the withdrawal of federal troops from the South, effectively ending Reconstruction and allowing for the establishment of Jim Crow laws.
- Plessy v. Ferguson was an 1896 Supreme Court case that upheld racial segregation under the "separate but equal" doctrine.
- Reconstruction Acts were pieces of legislation passed in 1867 that aimed to rebuild the South and guarantee rights for formerly enslaved individuals.
In summary, the correct answer is Black Codes.