The legal drinking age in the United States is 21 years old. This age limit was established by the National Minimum Drinking Age Act of 1984, which aimed to reduce alcohol-related traffic fatalities among younger people. States received federal highway funds only if they enforced this minimum drinking age. Prior to this law, many states had varying legal ages, causing confusion and inconsistency. The decision to set the age at 21 was influenced by studies showing that younger individuals are more likely to engage in risky behaviors, including drunk driving. The law is still debated today, with arguments regarding its effectiveness and calls for potential modifications.