All 50 US states have set their minimum drinking age (MLDA) to 21 although exceptions do exist on a state-by-state basis for consumption at home, under adult supervision, for medical necessity, and other reasons.
Proponents of lowering the MLDA from 21 argue that it has not stopped teen drinking, and has instead pushed underage binge drinking into private and less controlled environments, leading to more health and life-endangering behavior by teens.
Opponents of lowering the MLDA argue that teens have not yet reached an age where they can handle alcohol responsibly, and thus are more likely to harm or even kill themselves and others by drinking prior to 21. They contend that traffic fatalities decreased when the MLDA increased.
Each state was allowed to set its own alcohol consumption laws following the adoption of the 21st Amendment on Dec. 5. 1933. The amendment repealed alcohol prohibition. 
Most states established 21 as the minimum legal drinking age (MLDA). However, Illinois and Oklahoma set the MLDA at 21 for men and 18 for women in 1933. In 1976, the US Supreme Court ruled that the gender disparity violated the Equal Protection Clause of the 14th Amendment in Craig v. Boren. 
When the 26th Amendment was passed on July 1, 1971, which lowered the legal voting age from 21 to 18 years old, 30 US states lowered the MLDA to 18, 19, or 20. By 1982, only 14 states still had a MLDA of 21. 
Reports in the 1970’s showed that teenage car accidents increased in states where the MLDA had been lowered from 21, which prompted Congress to pass the National Minimum Drinking Age Act of 1984. 
The Act did not require a national MLDA of 21, but it effectively mandated it by stipulating that some federal transportation funds would be withheld from states that failed to make 21 their minimum age for purchasing and publicly possessing alcohol. Since 1984, all states that had previously lowered their MLDA from 21 have all raised their MLDA back to 21. South Dakota and Wyoming were the last states to do so in 1988. 
The consumption of alcohol by people under 21 is generally illegal across the United States. However, some states have set exceptions that allow underage consumption of alcohol in certain circumstances. For example, underage drinking is allowed in some states if done on private premises with parental consent, for religious purposes, or for educational purposes. Some states also allow prosecutorial exceptions if a minor who has consumed alcohol is reporting an assault or medical emergency for themselves or another person.
The debate about MLDA often references the “age of majority.” According to the Law Information Institute at Cornell University, the “age of majority refers to the age at which an individual will be legally considered an adult. It is the age at which one will be subject to the full legal rights and responsibilities of an adult, including the right to vote, the right to join the military or the right to sign a contract. After reaching the age of majority, one will become fully responsible for their own actions, contractual obligations and other undertakings. Parental duties of support will also cease.” Most countries have set the age of majority at 18, however, in the United States, the age of majority is 19 in Alabama and Nebraska and 21 in Mississippi. Many question why a person may enlist in the military or smoke cigarettes legally, but may not consume alcohol at 18 years old. 
The discrepancy between the MLDA and the age of majority–and its many responsibilities and authorities–along with continued incidents of alcohol abuse reported on college campuses have fueled debate on whether setting the MLDA at 21 is fair, smart, or effective. In 2008, 136 college and university presidents signed a statement via the Amethyst Initiative that argued “21 is not working,” citing binge drinking, fake IDs, and the fact that adults age 18-20 are able to vote, serve on juries, and enlist in the military. 
Globally, of 194 countries the MLDA is most often 18 (109 countries), followed by 17 (17 countries), 21 (13 countries including the US), 16 (11 countries), 20 (5 countries), and 15, 19, and 25 (one country each). 18 countries had no MLDA and 11 had total bans. The remaining countries had mixed MLDAs for types of alcohol or place of consumption, no information, or subnational MLDAs (like the US, though the US is uniform and thus counted as 21).
According to the World Health Organization the “harmful use of alcohol” is responsible for 3 million deaths every year (5.3% of all deaths globally), with 13.5% of all deaths of 20-39 year olds attributable to alcohol. Misusing alcohol is also found to be the causal factor in over 200 diseases and injuries, accounting for 5.1% of the “global burden of disease.” 
|Teens Vaping More; Drinking, Smoking, and Using Opioids Less|
|Should the Voting Age Be Lowered to 16?|
|Social Media Increases Teen Girls’ Exposure to Bullying|