Silverthorn, a
Democrat, was elected
Marathon County District Attorney in 1864, and re-elected twice. In 1867 he was elected to the Assembly district which encompassed both Marathon and
Wood Counties, succeeding fellow Democrat
George Hiles; he was assigned to the
standing committees on
school and
university lands, and on
enrolled bills. He was succeeded for the 1869 term by another Democrat,
Henry Reed. In 1873 he was again elected to the Assembly for a one-year term (the district now consisted solely of Marathon County) to succeed his banking partner
Daniel L. Plumer, this time as a "Liberal Democrat". Like Plumer, he was part of the
Reform Party, a short-lived
coalition of Democrats,
reform and
Liberal Republicans, and
Grangers formed in 1873. He was assigned to the committees on the
judiciary and on
elections. In 1874 he was elected to the State Senate from the
21st District (Marathon,
Oconto,
Shawano and
Waupaca counties and parts of
Outagamie County) as a Liberal Democratic/Reform candidate, with 4693 votes to 3968 for
Stalwart Republican Elisha L. Bump, for a two-year term; he was assigned to the committees on the judiciary and on
federal relations in the first year, moving in the next session from federal relations to the committees on
banks and
banking, and on
privileges and
elections. He was not a candidate for re-election, and was succeeded by another Liberal,
Henry Mumbrue. In 1884, with the Reform Party having collapsed, Silverthorn ran as the Democratic nominee for
Attorney General of Wisconsin, coming in second to
Leander Frisby in a four-way race (Frisby 162,167; Silverthorn 145,018; 8313 for
Prohibitionist F. M. Angel; and 4261 for
Greenbacker M. W. Stevens). In 1896, he was the Democratic nominee for
governor, losing to
Edward Scofield in a five-way race. in January 1897 he was the Democratic candidate for
United States Senate; he was defeated by
John Coit Spooner, the Republican candidate; he was also opposed by Gold Democrats such as
Jesse Clason (who voted for Spooner) and
Albert Solliday, who cast a
protest vote for
William Freeman Vilas. In 1903, Scofield appointed Silverthorn to a
Wisconsin Circuit Court seat; he was re-elected in 1904, defeating old rival Elisha Bump. ==Leaving public life==