In the latest files released by familysearch I found Elizabeth M CUMPSTON a widow of Veteran William H CUMPSTON of the 12 Illinois Infantry Company B Application no. WC30401
[Case Files of Approved Pension Applications of Widows and Other Dependents of Civil War Veterans, ca. 1861-ca. 1910 Record Group 15 ARC 300020]
I have a William H CUMPSTON on my website at http://www.cumpston.org.uk/#/william-h-cumpston-boone-co-i/4539297773 who was killed in the War and another of the same name at
http://www.cumpston.org.uk/#/william-h-cumpston-lucas-co/4539297678 who was mustered out. Do let me know if you recognise these people.