John Aaron Rawlins was born in Galena, Illinois, on February 13, 1831. He received little education as a child, but later studied in a law office and was admitted to the bar in 1854. Practicing law in Galena, he became city attorney in 1857 and was nominated a presidential elector for Stephen A. Douglas in the 1860 election. After the Civil War began, Rawlins joined Brig. Gen. Ulysses S. Grant's staff, and served as adjutant through the war.
In addition to issuing orders for Grant and helping with correspondence, Rawlins headed Grant's military household. Near the end of the war, he tended to go beyond the boundaries of his position, even trying to interfere with Maj. Gen. William T. Sherman's Georgia Campaign. By the end of the war, Rawlins was a brigadier general (as of August 11, 1862); and held the new title of chief of staff of the army (as of March 3, 1865).
When Grant became President, Rawlins remained with him, and insisted on being appointed Secretary of War. Rawlins died on September 6, 1869, in Washington, within six months of receiving the appointment.