Jacob Detwiler married Caroline Himmelwright July 10, 1845, and, in 1860, was a clerk living in Harrisburg, Dauphin County, Pennsylvania. He stood 5' 7" tall and had dark hair and brown eyes.
A Civil War veteran, he enlisted in Harrisburg September 9, 1861, and mustered into federal service at York September 14 as captain of Co. B, 87th Pennsylvania Infantry. A poor disciplinarian, he was unpopular with his men, who often made a fool of him. (See Dennis W. Brandt, From Home Guards to Heroes: The 87th Pennsylvania and its Civil War Community for a full accounting.) A board of doctors recommended he be discharged, and he resigned officially due to "valvular disease of the heart." Nonetheless, he assumed command of a company in the 53rd U.S. Colored Troops but was dismissed from the unit. He then recruited a company with the 99th Pennsylvania Infantry that transferred to the 199th Pennsylvania Infantry September 24, 1864, but he was discharged December 29, 1864, and never assumed an active command roll. The army gave every indication of simply not wanting him in command of men.
After the war, he and Caroline moved to Chicago, but Caroline moved to Polo, Ogle County, where Jacob had some investments and had done well financially in the coal market. Caroline returned to Harrisburg and was living there in 1890. Jacob remained in Illinois and was buried by the Blair Lodge #393, A.F. & A.M.