In 1844, Washburn moved to Woodstock and formed a partnership with Charles P. Marsh, which they maintained until Washburn's death in 1870. Also in 1844, Washburn was elected reporter of decisions of the Vermont Supreme Court, a position he held for eight years. He represented Woodstock in the Vermont House of Representatives from 1853 to 1855. Washburn was also involved in civic causes, including becoming active in the temperance movement. He became active in the Republican Party in 1855; he was a delegate to the 1860 Republican National Convention, and served as chairman of the Vermont delegation.