Gretchen,

Mallisa (sic) and Alice are in the 1870 Census of Clark in the HH of Nancy J. However, there is no record of a daughter named Nancy. The 1860 census apparently used nicknames and/or phonetic spellings with Elisa for Mallisa and Alena for Melvina. Alice and Alex may have sounded alike and the census-taker wrote the full name as Alexander. This is par for 1790-1870 census which were done by political appointees.

Mallisa Blanton Dennison's obituary is at Findagrave.com (Fresno County, CA). Melvina Blanton Hysell died in Blaine OK and her grave is there also, along with her husband. It is easy to get death certificates in OK for genealogical purposes. It is not that hard in CA, but I do not know if they listed more than the mother's maiden name for parents.

The MO death certificates are online, but only begin statewide in 1910. There are some before then.

http://www.sos.mo.gov/archives/resources/deathcertificates/

Bob