[1] In the 1844 United States presidential election, Thompson cast his vote for Whig Party candidate Henry Clay.
Thompson began traveling westward in 1854, settled in Davenport, Iowa, by 1855, and formed a law firm with partner H. G. Barber (or Horatio B. Barner).
Thompson continued to be politically active in Iowa, and joined the emerging Republican Party.
He served a one-year term, and was subsequently named city attorney under mayor John E. Henry in 1881.
[1] John W. Thompson married Westmoreland County, Pennsylvania, native Margaret A. Wallace on May 12, 1874, until she died on March 12, 1875.