Enlisted from Excelsior, Sauk County, Wisconsin and mustered in on 10 May 1861, Company A, 6th Wisconsin Volunteer Infantry Regiment as a Private; absent due to illness and hospitalization in November, 1861 *; mustered out with disability on 2 May 1862. Re-enlisted from Excelsior,Sauk County and mustered in on 8 February 1865, Company E, 49th Wisconsin Infantry as a Corporal; mustered out on 8 November 1865 at St Louis, Missouri.

* "Clinical Records of Continued Fevers -- Typho-Malarial and Typhoid Fever -- Case 66. — Chill and remitting fever; rose-spots on 12th day; drowsiness; sordes; cough; diarrhoea and iliac tenderness; record unfinished. — Private J. M. Foster, Co. A, 6th Wis. Vols.; age 21; was admitted Nov. 1, 1861, as a case of typhoid fever. Late in September he had measles, and on October 24 was taken with a chill followed by fever, weakness, anorexia, pain in the back and bones, nausea, vomiting and diarrhoea, which continued up to the date of his admission. He said he felt better about noontime daily. On November 2 he was dull, his eyes slightly suffused, pulse 112, quick and of fair strength, skin soft and moist, tongue soft, coated in the centre and at the tip, teeth covered with sordes; he had anoexia, much thirst and a diarrhiea of four stools daily, with some abdominal tenderness and some cough. Quinine in five-grain doses was given three times daily. Next day his condition was unchanged but on the 4th the pulse became reduced to 100 and lost its quickness and strength, the skin was hot and covered with minute rose-colored spots, the tongue moist and brown, eyes injected and the respiration labored. The patient continued dull and drowsy on the 6th, and the diarrhoea persisted, with some tenderness in both iliac legions; but the tongue appeared cleaner at the edges and the repiration was natural. On the 7th the pulse was 108 and weak, the skin dry, husky and covered with rose-colored spots, the tongue dry and brown, the gums and teeth blackened, the bowels loose, tympanitic, tender and gurgling on pressure. The record leaves the patient in this condition on the 8th, and closes with the remark that he was transferred to Philadelphia, Pa., Feb. 15, 1862." -- The Medical and Surgical History of the War of the Rebellion. Part III, Volume I. (3rd Medical volume) by U. S. Army Surgeon General's Office, 1888.