Final answer:
The National Minimum Drinking Age Act of 1984 sets the legal age for purchasing alcohol in the United States at 21 years old.
Step-by-step explanation:
According to the National Minimum Drinking Age Act of 1984, people are allowed to purchase alcohol at the age of 21. This Act required states to raise their minimum drinking age to twenty-one or face a loss of a significant amount of federal highway funds. The purpose of this legislation, supported by organizations such as Mothers Against D runk Driving (MADD), was to reduce alcohol consumption among youths and to combat intoxicated driving.
While there are criticisms and comparisons to foreign nations with more liberal alcohol laws, the legal age for purchasing alcohol in the United States is firmly established at 21.