James M Cunningham son of William and Elizabeth Cunningham born abt 1839 TN wife Serilda born abt 1841 Iowa are all iving together in Webster Co MO in 1860. (Family with Annanias and Margaret are all found together in Wright Co 1850 census)
As mentioned Service card for Webster Co Home Guard is here:
http://www.sos.mo.gov/TIF2PDFConsumer/DispPDF.aspx?fTiff=/archives/AdjutantGeneral/Civil_War/ServiceCards/s886/2212.tif&Fln=S89581.pdf
Next likely hit is
http://www.sos.mo.gov/TIF2PDFConsumer/DispPDF.aspx?fTiff=/archives/AdjutantGeneral/Civil_War/ServiceCards/s909/0474.tif&Fln=S89592.pdf
Can't prove for sure but enlistment dates, muster out dates, age, and geography all match to make sense and answers your question in the right time frame. You infer that Serilda filed for a pension that file should have info on what happened to him....
John R.