The Willis Tower, formerly known as the Sears Tower, is a 110-story building designed by Bruce Graham of the firm Skidmore, Owings & Merrill. The building is a modernist rendition of base, middle, and top that clearly illustrates the goals of the original client Sears, Roebuck & Company: housing 5,000 Sears employees in the base, leasing the middle to tenants, and using the top to establish the world’s tallest building at the time of completion for the world’s largest retailer at the time.