When did they change the drinking age to 18?

After prohibition was repealed, most states established a minimum legal drinking age of 21. However, after the 26th amendment was ratified (which lowered the voting age from 21 to 18), a large number of states reduced the drinking age to 18 to reflect the change in the legal age of majority. In 1984 Congress passed the National Minimum Drinking Age Act which withheld federal funds from states who did not adopt a legal drinking age of 21. There was political push back on the state level. For example, the Louisiana Supreme Court ruled the law unconstitutional and lowered the drinking age back to 18 for a short time in the mid-90s. Eventually every state fell in line in order to receive federal highway funds. Still, there remain states in which consumption of alcohol by persons under 21 is not explicitly prohibited and exceptions are made for consuming alcohol in private residences.