Knox was elected as a Whig to the Thirty-third Congress in and reelected as an Opposition Party candidate to the Thirty-fourth Congress (March 4, 1853 – March 3, 1857). He served as chairman of the Committee on Roads and Canals (Thirty-fourth Congress).
Knox was elected to the Thirty-third Congress as a Whig and then re-elected for the Thirty-fourth Congress (March 4, 1853 – March 3, 1857). He held the role of chairman of the Committee on Roads and Canals in the Thirty-fourth Congress.