Why is the U.S. drinking age 21?

The drinking age is 21 in the United States because of federal legislation enacted in 1984, known as the National Minimum Drinking Age Act. This act pressured states into raising their minimum legal drinking age (MLDA) to 21 by dictating that a portion of their federal transportation funding would be withheld if they did not comply. Before the act, the MLDA varied and was as young as 18 in some states and 21 in others. Nationwide standardization was a direct response to concerns about traffic fatalities among young people, particularly those younger than 21, who were statistically more likely to be involved in alcohol-related crashes: Reports in the 1970s indicated an increase in car accidents involving teenagers in states where the drinking age had been lowered. After the act was passed, states began to raise the MLDA to 21; all had done so by the end of 1988. The National Highway Traffic Safety Administration estimates that having the MLDA set at age 21 saved more than 31,000 lives from 1975 to 2016.