How old is citizens have to be to vote for president?

For most of U.S. history Americans had to be at least 21 years old to vote. At the time of the Vietnam War, during the 1960s and 70s, many people thought that people who are old enough to fight in a war should also be old enough to vote. In 1971, the 26th amendment changed the minimum voting age from 21 to 18 for all federal, state, and local elections.