Which amendment gave freed slaves the right to vote?

The 15th Amendment (XV) to the Constitution guaranteed the right to vote not be denied to anyone based on "race, color, or previous condition of servitude." It was ratified in 1870, and was the last of the three so-called "Civil War Amendments", following the 14th (XIV) in 1868 and the 13th (XIII) in late 1865 (after the war was over).