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The architect responsible for the iconic Willis Tower (formerly Sears Tower) in Chicago was Fazlur Rahman Khan, a Bangladeshi-American structural engineer and architect who rose to prominence as a partner at Skidmore, Owings & Merrill (SOM), a renowned architectural firm known for its influential contributions to skyscraper design and engineering. SOM is headquartered in Chicago and holds a distinguished reputation for crafting several other notable landmarks within the city.