The African American vote encapsulates the dynamism that is American politics. Blood was shed and lives were lost for African Americans to secure the right to vote. Even today, guaranteed access to the ballot is more a myth.
Prior to the Civil War a handful of free blacks in northern states exercised their right to vote but they were too few in number to make a difference in anything but the smallest of local elections. Then, in the immediate aftermath of the Civil War, southern states enacted a variety of Black Codes, precursors to post-Reconstruction Jim Crow. These effectively codified all manner of discrimination against newly freed slaves. In response to this, Republicans in Congress passed two of the three Civil War Amendments, the 14th amendment of 1868 and the 15th amendment of 1870. The 14th provided citizenship guarantees (thus overturning the notorious Dred Scott decision) and the 15th provided voting rights for black men.
For a time the 15th led to real change in Southern politics. By the dozens, black men won seats in state legislatures and even a few went to Congress. In fact, the first black elected to the U.S. Senate, Hiram K. Revels, came from the closed society of Mississippi. This political renaissance had an unfortunately short life. Northerners preferred national unity over the needed occupation required to guarantee the political rights of black citizens. So, once Union troops withdrew from the South, unreconstructed Southern Democrats resumed their racial tyranny.