Costco (Costco) is the United States is a large chain of membership warehouse stores, founded in 1976 in San Diego, California Price Club, seven years later in Seattle, Washington founded Costco, in 2009 is the third largest retailer in the United States, the ninth largest in the world. Costco is the founder of the members-only warehouse wholesale club, which has been committed to providing members with high quality branded goods at very low prices possible. Costco has more than 500 stores in seven countries around the world.