Monfils was born on December 12, 1938, in Green Bay, Wisconsin. He attended Ss Peter and Paul School (Green Bay), Sacred Heart Seminary (
Oneida, Wisconsin),
St. Norbert College (
De Pere, Wisconsin), and
Loyola University (Chicago). He served as a lieutenant in the
United States Army in Germany from 1961 to 1963 and on active reserve with the
United States Army Reserve from 1964 to 1967. Monfils married Mary Peterson in 1967. They had two children. He married Mary Timney in 1986. Monfils worked for
Fort Howard Paper Company in Green Bay and was a partner in a direct mail marketing business and a cable television franchise group. After Monfils and his second wife moved to Ohio, he worked for more than 10 years as a labor mediator for the state of Ohio. Monfils died on May 11, 2021, in
Peekskill, New York. He was 82. ==Political career==