After the Civil War, the United States was deeply divided, both politically and economically. The Republican Party had been in power since 1861, and they had been instrumental in pushing through the Reconstruction amendments to the Constitution. These amendments had given African Americans the right to vote, and had also given the federal government more power over the Southern states.
The Democratic Party was opposed to many of the changes that the Republicans had made, and they began to gain strength in the South. In 1876, the Democratic candidate for president, Samuel J. Tilden, won the popular vote, but the election was disputed, and the Republicans were able to eventually secure the victory for their candidate, Rutherford B. Hayes.
In the Compromise of 1877, the Republicans agreed to remove federal troops from the South and to allow the Southern states to control their own affairs. This effectively ended Reconstruction, and the Southern states were able to pass laws that were discriminatory to African Americans, such as the Jim Crow laws.