What new opportunities were available to Africa American after Civil War?
They were emancipated and became normal citizens
Following the Civil War, African Americans were emancipated by the 13th amendment, they were granted citizenship by the 14th amendment(1868), and were granted the right to vote by the 15th amendment in 1870.
Following the end of Reconstruction in 1877(with the election of Hayes), these advances were ruined and Segregation became a formal institution in the South with the so-called "Jim Crow" laws. It was declared constitutional by the 1896 Plessy vs Ferguson Supreme Court decision.