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
Library Tower (Chicago) Associates. Library Tower (Chicago) Library Tower Chicago is located on 520 S. State Street, Chicago, Illinois, which is the block directly south of the main branch of the Chicago Public Library in the Loop community area. Currently (4/2009) the building has 184 Units. 52 units have been sold and closed. Another 36 are under contract. Apparently, the building was mostly sold unit the economy forced investors to pull out of the building, leaving it largely unsold. Units have been on sale since 2005, with closing first occurring in 2008. There has been substantial price drops from being on the market