Jefferson was the son of Thomas Keeney Mitchell and Elizabeth Ann Roe and the grandson of Richard Mitchell and Ruby Keeney.

He married Clara Beach on June 9, 1866 in Plainfield, Waushara, Wisconsin.

Four known children were born to this union:
Charles Mart Mitchell 1867 – 1891
Maude Elizabeth Mitchell Prince 1870 – 1918
Guy Winters Mitchell 1877 –
Thomas Walter Mitchell 1878 –

U.S. Civil War Soldier Records and Profiles
Name: Jefferson B Mitchell
Residence: Benton, Wisconsin
Enlistment Date: 14 Oct 1864
Rank at enlistment: Private
State Served: Wisconsin
Survived the War?: Yes
Service Record: Enlisted in Company I, Wisconsin 1st Heavy Artillery Regiment on 14 Oct 1864.
Mustered out on 10 Feb 1865.
Sources: Roster of Wisconsin Volunteers: War of the Rebellion

"Jefferson Button Mitchell

J. B. Mitchell Passes Away

Another pioneer resident of Plainfield has gone to his long home, and another name is unanswered at the roll call of the veterans of the Civil War. Thursday last, May 14, 1903, Jefferson B. Mitchell, generally known as "Jack" Mitchell among his many friends here, died at Ashland, Wisconsin, where he had resided for several years past. The remains were brought here Saturday and brief funeral services were held at the Baptist Church, Rev. C. W. Powell."

From the 1881 History of Northern Wisconsin: Plainfield Biographical Sketches

"JEFFERSON B. MITCHELL, proprietor of the Mitchell House, Plainfield (WI), was born in Tioga, Penn., March 31, 1837, and lived there until 1864 with his parents on a farm. He began clerking in a store at seventeen years of age, and remained in that capacity for his father, Thomas K. Mitchell, and others, about ten years. He came to Plainfield in 1864, where he lived about nine years engaged in the mercantile business. He was elected County Treasurer in 1872, and served one term. He went to Centralia afterward, and took charge of a dry goods store two years; then he engaged in the mercantile business for himslef for eighteen months; he then returned to Plainfield and engaged in the same business, and in buying grain, etc., in company with Mr. L.S. Walker, which was continued about three and a half years. In the srping of 1880, he began the erection of his hotel, a large brick building, and began business in it in December, 1880. He was married in Plainfield June 9, 1866, to Clara B. Beach, who was born in Canada West, June 16, 1847; they have had four children, named Charles M., Maude E., Guy W., and Thomas W. Mrs. Mitchell died July 19, 1881. Mr. Mitchell enlisted in Co. I, 1st W.H.A., Oct. 14, 1864, and was discharged Feb. 10, 1865."