On Monday, September 15th, 1845
[McLean County Circuit Court opens six-day session at Bloomington.] On or about this day, Lincoln signs, with 51 others, mostly lawyers and citizens of Bloomington, petition to Gov. Ford asking reprieve for person whose name court does not know, who is sentenced to serve one year for larceny by McLean Circuit Court at this session. Petition for Pardon of a Person Unknown, [15?] September 1845, CW, 1:346-47.

Related sources from The Collected Works of Abraham Lincoln

Petition for Pardon of a Person Unknown

Lincoln Timemap for 1845