From the 1920s to the 1950s, Sears built many urban department stores in the U.S., Canada, and Mexico (apart from, but not far from, existing central business districts), and they overshadowed the mail-order business. Starting in the 1950s, the company expanded into suburban markets and malls in the 1960s and 1970s. In 1959, it had formed the Homart Development Company for developing malls. Many of the company's stores have undergone major renovations or replacement since the 1980s. Sears began to diversify in the 1930s, creating Allstate Insurance Company in 1931 and placing Allstate representatives in its stores in 1934. Over the decades it established major national brands, such as Kenmore, Craftsman, DieHard, Silvertone, Supertone, and Toughskins. The company became a conglomerate during the mid-20th century, adding Dean Witter and Coldwell Banker real estate in 1981, starting Prodigy as a joint venture with IBM in 1984, and introducing the Discover credit card in 1985.