Simmons was born on May 3, 1931. He attended Massachusetts Institute of Technology (MIT) in 1949.  He became a metallurgist at the Allegheny Ludlum Steel corporation in Pittsburgh. He then worked for other steel companies before returning to become the chief executive of Allegheny, taking it public and then leading a management buyout.  Having become wealthy, he then created a variety of endowments at MIT.
Simmons was also chairman of the Pittsburgh Symphony Orchestra between 1989 and 1997. He returned as chairman in 2003 until his retirement in 2015.