He soon afterwards began to take a warm interest in the municipal affairs of Toronto, and in 1855 was elected an Alderman of the city. In 1859 he was Mayor of Toronto, and was the first Chief Magistrate elected by popular suffrage. In 1856 he was appointed a Commissioner for the consolidation of the public general statutes of Canada and Upper Canada respectively.
In politics Mr. Wilson was a member of the Reform Party, and had frequently been importuned to allow himself to be put in nomination for a seat in the Legislature. Being much occupied with professional and municipal affairs he had declined such importunities, but upon the death of Mr. Hartman, the member for the North Riding of the county of York in the Canadian Assembly, on the 29th of November, 1859, that constituency was left unrepresented, and Mr. Wilson, being again pressed to enter political life, contested the representation of North York, and was returned at the head of the poll. He took his seat in the House as an avowed opponent of the Cartier-Macdonald Administration. He was again returned by the same constituency at the next general election. In 1861 he was an unsuccessful candidate for the representation of West Toronto. Upon the formation of the Sandfield Macdonald-Sicotte Administration, in May, 1862, he accepted office therein as Solicitor-General, and was reëlected by his constituents upon presenting himself to them. He held the portfolio of Solicitor-General, with a seat in the Executive Council, until the month of May, 1863. On the 11th of the month he was elevated to a seat on the Judicial Bench as a Puisné Judge of the Court of Queen's Bench for Upper Canada. Three months later (on the 24th of August) he was transferred to the Court of Common Pleas, where he remained until Easter Term, 1868, when he was again appointed to the Queen's Bench, as successor to the Hon. John Hawkins Hagarty, who had been appointed Chief Justice of the Common Pleas. In 1871 Judge Wilson was appointed a member of the Law Reform Commission. In the month of November, 1878, he was himself appointed Chief Justice of the Court of Common Pleas, a position which he now occupies.
While at the Bar he was regarded as second to no man in the Province in certain branches of his profession; and his reputation has rather grown than diminished since his elevation to the Bench. His learning, judicial acumen and perfect impartiality are acknowledged by the entire profession of this Province, as well as by his brethren on the Bench.