Sears (officially Sears, Roebuck & Company) is a chain of American department stores. The company was founded by Richard Warren Sears and Alvah Curtis Roebuck in 1886; it was previously based in the Sears Tower in Chicago, and is currently headquartered in Hoffman Estates, Illinois. It began as a mail order catalog company, and began opening retail locations in 1925. The company gradually declined following prosperity during the second half of the twentieth century, and was ultimately purchased by the American discount store chain Kmart in 2005, which 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.