William Willison/Wilson
Illinois Civil War Muster and Descriptive Rolls Database (Illinois State Archives):
       Willison, William  - Pvt - Co I - 2 IL US L ART
        Residence, Joliet, Will Co, IL; Join, 01Oct1861-Joliet; Age, 40; Born, NJ
        Height, 5' 6"; Hair, black; Eyes, hazel; Complexion, dark; Married; Boatman
        Reenlisted as a veteran
        Wilson, William - Pvt - Co I - 2 IL US L ART
         Residence, Joliet, Will Co, IL; Join, 01Jan1864-Chattanooga,TN; Age, 42; Born, NY
         Height, 5' 6"; Hair, black; Eyes, hazel; Complexion, light; Boatman
         Mustered out, 14Jun1865, Springfield
American Civil War Soldiers (ancestry.com)
      
Civil War Soldiers & Sailors System Search Detail (National Park Service):

National Graves Registration Database (Sons of Union Veterans of the Civil War):
      
Will County Illinois USGenWeb Necrologist Reports (© 2002 The ILGenWeb Project All Rights Reserved):

Headstone Reading,

Published Obituaries:

Additional Biographical/Historical Material:
                     Regimental and Unit Histories - Illinois Adjutant General's Report
      Battery I [2nd Illinois Light Artillery] was recruited in Will county, and was mustered into the United States service at Camp Butler, December 31, 1861.  . . .
 
      January 1, 1864, all of the old members were mustered out and re-mustered in as veterans, and arrived at Springfield, Ill., January 16, where they were given thirty days’ furlough and ordered to report for duty at Joliet, Ill.  . . .

      Upon the surrender of General Johnston's Army [26Apr1865], it proceeded to Washington, and took part in the grand review, and from there was ordered to Springfield, Ill., to be mustered out of service.