As you know our U.S. Constitution has 27 Amendments. The process of Amending the Constitution is explained in Article V of the document itself.
The 27th , and last approved Amendment, was submitted by James Madison along with what became our Bill of Rights. It’s a good one and it finally received approval of Michigan, the last needed state, on May 7, 1992. It says that Congress can’t give itself a raise unless a national vote has intervened before one can be granted. Why didn’t that pass with the other 10 Amendments of the Bill of Rights? I dunno.
The 26th Amendment lowered the voting age to 18 and was approved finally on July 1, 1971. But it was submitted to the States long after the Bill of Rights! In March of 1971. How things have changed, including our Constitution.