William S. McKinnon was born at Owen Sound, Canada West.

[3] In 1880, he was the founder and head of the McKinnon Iron Works Company at Ashtabula Harbor.

[2] McKinnon was elected to the Ohio House of Representatives in 1897 and served in the 73rd, 74th, and 75th General Assemblies, 1898–1903.

Elections were moved to even-numbered years, and McKinnon chose not to run in 1908.

His term would have ended in January 1909, but he died at his Ashtabula home on November 17, 1908.