When is the last time the US Constitution was amended?

The last amendment to the United States Constitution was the Twenty-Seventh Amendment, which does not allow Congress to have any changes to their compensation until after the next election in the House of Representatives. The purpose of this amendment to prevent Congress from giving themselves a pay raise in the same session.
It was first proposed by James Madison in 1789 during the first Congress. Although Congress immediately passed the amendment, only six states ratified it. It would take over 200 years for the required three-fourths states to ratify the amendment, and it was not added to the Constitution until 1992.
The six states that initially ratified the amendment in the late-eighteenth century were Maryland, Delaware, North Carolina, South Carolina, Vermont, and Virginia. Michigan became the 38th state in 1992, which gave the amendment the three-fourths majority it needed for ratification.