A solicitor by profession he had an office in Wellington Street, Ballymena. With a keen interest in local affairs he became a member of the Ballymena Urban Council in 1926. The impression he made there was amply demonstrated when the following year he was elected vice-chairman and in 1928 Chairman. He was chairman again in 1933, 1936 to 1938 and when Ballymena was elevated to the status of a borough in 1939 William Shaw was unanimously elected as the Borough’s first Mayor. In 1945 he was elected Freeman of the Borough. He also represented Ballymena on the Antrim County Council for nine years and was also a J.P.
William Shaw died at his home, Mountstewart, Cullybackey Road, on 31st July 1951 and was interred in Cullybackey beside the church where he had served as secretary for forty-six years.