He was a school trustee from 1925 to 1938, and served as mayor of the Town of Morris from 1948 to 1954, coinciding with his early period in the legislature.
[1] At that time, Manitoba was governed by a coalition of the province's Liberal-Progressives (commonly called Liberals) and Progressive Conservatives.
Shewman ran as an independent candidate in Morris, and defeated coalitionist John C. Dryden by 153 votes.
In 1950, Shewman called on Premier Douglas Campbell to declare a state of emergency over rising flood waters.
The Progressive Conservatives made significant gains in the 1958 provincial election, and formed a minority government after the vote.