Question: when did drinking age in us become 21

title: U.S. history of alcohol minimum purchase age by state
text: From 1976 to 1983 , several states voluntarily raised their purchase ages to 19 ( or , less commonly , 20 or 21 ) , in part to combat drunk driving fatalities . In 1984 , Congress passed the National Minimum Drinking Age Act , which required states to raise their ages for purchase and public possession to 21 by October 1986 or lose 10 % of their federal highway funds . By mid-1988 , all 50 states and the District of Columbia had raised their purchase ages to 21 ( but not Puerto Rico , Guam , or the Virgin Islands , see Additional Notes below ) . South Dakota and Wyoming were the final two states to comply with the age 21 mandate . The current drinking age of 21 remains a point of contention among many Americans , because of it being higher than the age of majority ( 18 in most states ) and higher than the drinking ages of most other countries . The National Minimum Drinking Age Act is also seen as a congressional sidestep of the tenth amendment . Although debates have not been highly publicized , a few states have proposed legislation to lower their drinking age , while Guam has raised its drinking age to 21 in July 2010 . 

Answer: answer: In 1984, Congress passed the National Minimum Drinking Age Act, which required states to raise their ages for purchase and public possession to 21 by October 1986 or lose 10 % of their federal highway funds.  By mid-1988, all 50 states and the District of Columbia had raised their purchase ages to 21 (but not Puerto Rico, Guam, or the Virgin Islands).  Guam has raised its drinking age to 21 in July 2010.