According to the Brewers Association a craft brewery is...
Small
Annual production of 6 million barrels of beer or less (approximately 3 percent of U.S. annual sales). Beer production is attributed to the rules of alternating proprietorships.
Independent
Less than 25 percent of the craft brewery is owned or controlled (or equivalent economic interest) by an alcoholic beverage industry member that is not itself a craft brewer.
Traditional
A brewer that has a majority of its total beverage alcohol volume in beers whose flavor derives from traditional or innovative brewing ingredients and their fermentation. Flavored malt beverages (FMBs) are not considered beers.
For more information on craft brewing, please visit the Brewers Association.