The amendment that lowered the voting age from 21 to 18 years old is the Twenty-sixth Amendment to the United States Constitution. It was ratified on July 1, 1971, and established the minimum voting age of 18 for all federal, state, and local elections in the U.S. This change was partly driven by the Vietnam War draft, which conscripted 18-year-olds to serve in the military while they were not allowed to vote. The amendment ensured that citizens 18 years and older could not be denied the right to vote based on their age.
