The 27th Amendment to the United States Constitution, regarding Congressional compensation, was the last amendment when it was ratified in 1992. But when was it first introduced in Congress?

James Madison, himself, first introduced the amendment relating to congressional pay back in 1789, along with 11 other amendments (10 of which became the Bill of Rights) but it never seemed to be a priority until public outcry over repeated congressional pay raises in the late 20th century sparked its final ratification in 1992.

This amendment simply said Congress could not vote themselves pay raises during the current session. Any raise they might vote to enact, would take effect during the next session, when many of them might not benefit from it.

Unlike other amendments, it had no time limit for ratification. So, the last amendment added to the Constitution happened to be one of the first proposed... it just took over 200 years to be added!