Thank you for the good suggestions. I will try contacting the cemetery.
I could not find either Richardson nor Mariah/Marie Boone in the 1921 Census. Perhaps they were visiting one of his children (at least 2 in New England). I looked at the interesting record you proposed for 1921 Census, but George W. Boone of Carleton (b. 1867) could not have been her son, as R. Boone was widowed in 1887 and married Mariah/Maria in 1894. I do not believe she had any children. The 78-year-old woman from 1921 could be Mariah/Maud/Marich. Found her in 1911 listed as Moria Boone, "aunt."
I appreciate the potential find and your willingness to assist.