Question: did the voting age used to be 21

Answer: Yes, The Twenty-sixth Amendment (Amendment XXVI) to the United States Constitution prohibits the states and the federal government from using age as a reason for denying the right to vote to citizens of the United States who are at least eighteen years old. The drive to lower the voting age from 21 to 18 grew across the country during the 1960s, driven in large part by (1) the military draft that resulted in young men between the ages of 18 and 21 being conscripted into armed forces, primarily the U.S. Army (or voluntarily enlisting, primarily in one of the other branches of the U.S. armed forces, to avoid the draft) to support military combat operations in Vietnam, and (2) the broader student activism movement protesting the Vietnam War. The impetus for drafting an amendment to lower the voting age arose following the Supreme Court's decision in Oregon v. Mitchell, 400 U.S. 112 (1970), which held that Congress may establish a voting age for federal elections, but not for local or state elections.