The piece of legislation that increased the number of eligible voters by decreasing the required voting age to 18 was the Twenty-sixth Amendment to the United States Constitution. The amendment was ratified on July 1, 1971, and lowered the voting age from 21 to 18 years old. This amendment was passed in response to the high number of young people who were drafted to serve in the Vietnam War, but were not allowed to vote in elections. The amendment was a major milestone in expanding voting rights and ensuring that all citizens, regardless of age, had a voice in the political process.