He traveled west to Lebanon, St. Clair County, Illinois to attend McKendree College, and graduated in 1862.

After the war, Wilkin married, as well as began studying law under the direction of John Scholfield in Marshall, Illinois.

Jacob Wilkin enlisted for three years, initially as a private in the 130th Illinois Volunteer Infantry Regiment.

Fellow soldiers elected him their captain, and by the time he was mustered out in August 1865, Wilkin had attained the rank of major.

As the war ended, he was transferred to the staff of General Ransom, and fought in the Battle of Fort Blakeley in Alabama in April 1865.

In 1888, he was elected to the Supreme Court of Illinois to fill the vacancy of John M. Scott, who had declined re-election.