Final answer:
The Twenty-Sixth Amendment granted 18-20 year olds the right to vote. It was enacted on March 23, 1971, in response to the Vietnam War draft situation, where young men could be drafted but not vote. Voter turnout in this age bracket has been historically low with few exceptions.
Step-by-step explanation:
The amendment that granted 18-20 year olds the right to vote is the Twenty-Sixth Amendment to the United States Constitution. Enacted on March 23, 1971, it prohibits any states or the federal government from using age as a reason to deny the vote to citizens of the United States who are at least eighteen years old.
The campaign to lower the voting age was particularly driven by the circumstances of the Vietnam War, during which young men who were eligible to be drafted at age 18 did not have the right to vote. This led to widespread protest and the rallying cry "old enough to fight, old enough to vote," culminating in the passing of the Twenty-Sixth Amendment to ensure that young adults had a voice in the democratic process.
Despite being able to vote, historical trends have shown that the voter turnout among voters aged 18 to 25 has generally been lower than other age groups, with some exceptions such as the increased turnout in the 2008 presidential election.