The Constitution initially only gave the right to vote to free white men.
The 15th Ammendment gave male citizens of any race the right to vote unless they were Native American.
The 19th Ammendment gave women the right to vote.
As a result of becoming U.S. citizens, Native Americans were able to vote for the first time in U.S. history.
Chicago gangster Al Capone's gang harassed voters, stuffed ballot boxes, and voted under ficticious names. They beat up voters who didn't agree with them, and even murdered party workers. The Chicago police - who got kickbacks from Al Capone - did nothing to stop the violence.
The 24th ammendment prohibited the use of poll taxes. Poll taxes were used after the Civil War in many Southern states. They made it difficult for African-Americans to vote by requiring poeple to pay a poll tax. Those who couldn't afford to pay the tax couldn't register to vote.
The Voting Rights Act banned the use of literacy tests. Making people take an impossibly difficult test was another way that Southern states tried to keep African-Americans from registering to vote after the Civil War.
The 26th Ammendment told both federal and state governments to lower the minimum voting age to 18.
As a result of this act, citizens can register by mail, when they obtain their driver's license, at government agencies, or download a voter registration form online.
In Shelby County v. Holder, the Supreme Court ruled that Section 4 of the Voting Rights Act was unconstitutional. This has led to changes in how states and localities with a history of discriminatory voting policies pass new voting laws and how these laws are overseen and objected to.