In regards to burial records, I called one of the local funeral homes and they are the ones that told me to try the courthouse.I haven't tried the Health Dept. yet.
I did find an obituary for William, but it has his name as "N.T.".It says he died March 17, 1927 at his daughter's house (Mrs. Ida Kercy) in Hingham, Montana.It also lists his other surviving children.The funeral home was "Fague & Fenn".I believe that funeral home is now known as Fenn Shirley & Stout.I can send you the obituary, if you want, it is in a .pdf file.
Do you know the exact date in October 1921 that Mary died?I can try to find an obituary for her, which may list the cemetery name.