William Woodburn was elected as a Republican to the Forty-fourth Congress, which met from March 4, 1875, to March 3, 1877. He was later elected to the Forty-ninth and Fiftieth Congresses, and he served from March 4, 1885, to March 3, 1889. He resumed the practice of his profession in Virginia City, Nevada. He was an unsuccessful candidate for election in 1892 to the Fifty-third Congress. He was appointed Attorney General of Nevada by Governor Reinhold Sadler on January 15, 1901, succeeding William D. Jones who resigned to become a state district court judge. Woodburn served the remainder of Jones' term which expired in January 1903, and returned to private practice.
Woodburn died on January 15, 1915, in Carson City, Nevada. He was interred in St. Theresa Cemetery.