For the person who just turned twenty-one, a completely new world of legal drinking opens up. For those already of drinking age, the twenty-one challenge is a fun excursion. Here is how it works, for the next twenty-one days in a row, visit a different beer bar! This is easy to do, if a person lives in San Diego, California, because it has some of the best beer bars and microbreweries in the United States. Take the Twenty-One Challenge, save a coaster or a napkin from each place and write the date on it to prove you were there.