Simpson began working as a clerk in at
Marshall Field & Co., beginning his work in the cashier's office and eventually becoming company head
Marshall Field's confidential clerk. After Field's 1906 death, Simpson was made the second Vice President of the company. He worked his way further to become the company's president and the chairman its board. During his time at Marshall Field's & Co., he also held directorships at the
Federal Reserve Bank of Chicago, the
New York Central Railroad, A.M. Castle & Co., Super Power Company of Illinois, the Western United Gas and Electric Corporation. In 1926, Simpson succeeded the retiring
Charles Wacker as the chairman of the
Chicago Plan Commission, a position he held for the next nine years. Simpson retired from his position at Marshall Field & Co. in 1932 and took a position as the chairman of
Commonwealth Edison. He held this position until his death. He also led the Public Service Company of Northern Illinois, the Commonwealth Subsidiary Corporation, and the Public Service Subsidiary Corporation. ==Personal life and death==