William Corning was born on August 29, 1829, in Mentor, Ohio.[1] His father died when he was five years old, but he still received an academic education.[2] He moved around central Ohio several times, going from Newark, to Hebron, to Columbus. He moved to Portage, Wisconsin, in October 1858, and by March 1859 he had established his hardward business.[2] He served on the city council, the school board, and the Columbia County board of supervisors.[1]
He was elected on the Democratic Party ticket to the Wisconsin State Assembly in 1871 from Columbia County's 1st Assembly district—at that time comprising the western part of the county.[1] He did not run for re-election in 1872.
He was elected mayor of Portage in 1875 and was re-elected to another term in 1876.[2]