In the post-Civil War era poll taxes were used by southern whites to disenfranchise African Americans. Poll taxes were also used to evade the Fifteenth Amendment and any other federal intervention.
Many African Americans and women viewed the poll tax as a gender and class issue that undercut the 15th and 19th amendments, while many southern political elites loved the poll tax because they could use it as discrimination.
The amendment was added because it was unconstitutional for poor men and women to not be allowed to vote, so they fully got rid of the poll tax. It allows everyone to vote no matter of how much money they had.
