Sears (officially Sears, Roebuck & Co.) is an American chain of department stores founded by Richard Warren Sears and Alvah Curtis Roebuck in 1886; it used to be based in the Sears Tower in Chicago, and is now headquartered in Hoffman Estates, Illinois. It began as a mail order catalog company, and began opening retail locations in 1925. The company was bought by the American big box chain Kmart in 2005, which had just emerged from bankruptcy at the time and renamed itself Sears Holdings upon completion of the merger. In terms of domestic revenue, Sears was the largest retailer in the United States until October 1989, when it was surpassed by Walmart. It is the fifth-largest American department store company by sales as of October 2013 (behind Walmart, Target, Best Buy, and Home Depot), and it is the twelfth-largest retailer in the country overall. It operates divisions in Canada and Mexico, among several subsidiaries within its brand.