There is no federal minimum age for serving alcohol. The minimum age to serve alcohol is determined by individual state alcohol laws that govern servers and bartenders, according to Alcohol Policy Information System.
Although the legal drinking age in the United States is 21, many states allow servers in restaurants to serve alcoholic beverages even if they are not yet 21. This is allowed on a federal level because servers are delivering drinks to others for consumption and not consuming the beverages themselves. Some states also distinguish between the types of alcoholic beverages that may be served by age. In other words, servers under 21 may serve beer but not wine or liquor.