Chicago Many other architects have left their impression on the Chicago skyline such as Daniel Burnham, Louis Sullivan, Charles B. Atwood, John Root, and Helmut Jahn. The Merchandise Mart, once first on the list of largest buildings in the world, currently listed as 44th-largest (), had its own zip code until 2008, and stands near the junction of the North and South branches of the Chicago River. Presently, the four tallest buildings in the city are Willis Tower (formerly the Sears Tower, also a building with its own zip code), Trump International Hotel and Tower, the Aon Center (previously the Standard
Merchandise Building forces with Sears-Roebuck & Co. of Chicago in forming a 50/50 ownership in a new company, Simpsons-Sears Limited. The new firm took control of Simpson's catalogue and mail-order business and would open new Sears-style department stores in markets not already served by Simpsons. It was seen as better suited to take on competition with the strong T. Eaton Co. catalogue business and to use Sears marketing principles to expand into smaller Canadian rural and suburban markets. The Toronto Mail Order Building complex - which eventually came to be known by the less cumbersome name of "the Mutual Street Building", continued