Aon Center (Chicago) the world headquarters of Aon and Amoco. Aon's US operations are still headquartered here. The building is also the co-headquarters of Kraft Heinz. The Standard Oil Building was constructed as the new headquarters of the Standard Oil Company of Indiana, which had previously been housed at South Michigan Avenue and East 9th Street. When it was completed in 1973, it was the tallest building in Chicago and the fourth-tallest in the world, earning it the nickname "Big Stan". (A year later, the Sears Tower took the title as Chicago's and world's tallest.) The building employs a tubular steel-framed structural system
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