Dunn was elected a member of the Indiana House of Representatives in 1848.[1] He was delegate to the state constitutional convention in 1850. He was elected as a Republican to the Thirty-sixth and Thirty-seventh Congresses. He served from March 4, 1859, until March 3, 1863. In 1860 during a campaign rally in Philadelphia, Dunn drew Lincoln's appreciation for publicly arguing Lincoln was "of the Old Hickory stamp," thereby making a favorable comparison to Andrew Jackson.[2] He served as chairman of the Committee on Patents (Thirty-seventh Congress). He was an unsuccessful candidate for reelection in 1862 to the Thirty-eighth Congress.
Following his unsuccessful bid to remain in Congress, Dunn accepted a military commission from the Governor of Indiana, fellow Republican Oliver P. Morton. He was a major and judge advocate general in the Department of the Missouri from March 13, 1863, until July 6, 1864. He was appointed lieutenant colonel and Assistant Judge Advocate General of the United States Army on June 22, 1864. This placed him second in rank in the Army's Judge Advocate General's Department, only behind General Joseph Holt.[3] At the end of the war, he was brevetted as a brigadier general dating from March 13, 1865.
Postbellum career
Grave of Dunn at Oak Hill Cemetery
Following the Civil War, Dunn stayed in the Regular Army. He was promoted to brigadier general and Judge Advocate General on December 1, 1875. He retired from the army on January 22, 1881.
^Joshua E. Kastenberg, Law in War, Law as War: Brigadier General Joseph Holt and the Judge Advocate General’s Department in the Civil War and Early Reconstruction, 1861-1865 (Durham, NC: Carolina Academic Press, 2011), 126
^Joshua E. Kastenberg, Law in War, Law as War, 126