His father fought in the Black Hawk War in Illinois in the 1830s, but afterward went to work on harbor improvements on Lake Erie and served two terms in the Michigan Legislature.

He was intent on becoming educated in the law, and, in 1848, began study in the offices of Isaac P. Christiancy, who would later serve as a justice of the Michigan Supreme Court and a United States senator.

[1] In 1849, Winfield moved west to Milwaukee, and was employed in the office of Emmons & Van Dyke, where he continued to study law.

[1] Shortly after his admission to the bar, he was appointed by United States District Judge Andrew G. Miller as a court commissioner and master of chancery in Milwaukee.

[1] In 1862, when James Henry Howe resigned his office to volunteer with the Union Army, Smith's former law partner, Governor Edward Salomon, appointed him to fill the vacancy as Attorney General of Wisconsin.

It involved extensive research and litigation, and was culminated in a negotiated agreement at Washington, D.C.[1] The American Civil War also loomed over his term as Attorney General, as he had to defend the constitutionality of the draft, and the Governor's powers to enforce it.

In 1871, he was elected to the Wisconsin State Assembly from Milwaukee County's 7th district on the Republican ticket,[2] though he did not actively pursue the office.

[3] His chief legislative accomplishment was the passage of a law which enabled the state school trust fund to loan money to the city of Milwaukee for the construction of water works, thus putting money to use that was otherwise sitting idle in state accounts, and enabling an important public improvement in the city.

He was urged to seek election to the Wisconsin Supreme Court on the death of Chief Justice Edward George Ryan, in 1880, but again declined.