The 15th Amendment to the U.S. Constitution extended the vote to black men in 1874. Some Southern states, fearing that freed slaves would use the power to vote to upset the status quo, worked around this law by adopting poll taxes -- no money, no ballot. This guaranteed that former slaves and poor people of any sort would not vote because they would not have enough money to pay the poll tax. The 24th Amendment made this practice illegal in 1964.