Re: Ann Woodworth-Mountcastle 1980 Pennsylvania
I don't know if you have made any progress in the last five years but there is an Anne Mountcastle listed in the Social Security Death Index as born 20 May 1904 and died Aug 1982. Her last residence was Pittsburgh. Henry Mountcastle is also listed as 23 Jan 1906 and died Sept 1977, also last lived in Pittsburgh.
I suggest trying to get their death certificates from the PA Div. of Vital Records in New Castle, PA. Since you are directly related you should be able to get them. You might also try getting their obituaries. Check with the Western Pennsylvania Genealogical Society at Carnegie Library in Pittsburgh to see if they can get them for you.
I also suggest asking your relatives for more information such as info on grandmother's siblings, where she was born, etc. Everything can be an important clue in finding her in historical records such as the census.