In the fall of 1855, Willson move to Ann Arbor to study at the University of Michigan medical department.

Willson joined and was active in two Civil War organizations: the Grand Army of the Republic and the Loyal Legion.

[4] On the death of Henry Crapo, the Willsons moved into the Crapo Mansion in Flint at First and Clifford (now Wallenberg Street) Streets, now known as Willson Park and part of the University of Michigan–Flint Campus.

As a trustee for the Michigan School for the Deaf, Willson served a six-year term.

[4] Willson became involved in businesses serving as Flint Gas Company's and Genesee County Savings Bank's president.