Missouri: Mershon, Murshon, Mashon, Merchant, etc.

Since first posting on this forum I have discovered that my wife's Mershon family had the surname spelled in several variations in local and government records: Mershon, Murshon, Machon, Mashon, Merchant, etc. I now know that William Mashon, who married Sonora Pullin in Platte Co., MO in 1869 was the son of Weeden and Margaret Mershon.

I am seeking information about the daughters of William and Sonora Mashon (Mershon). My wife's family believes the children--Mary, Kate (Annie?) and Margaret Melissa--were orphaned around 1891. We know that the youngest daughter, Margaret Melissa, went to live with an aunt and uncle Hickman in Clinton Co., MO around 1891. Margaret Melissa married Peter Luther Alumbaugh in Clinton Co., MO in 1897. At the time of her marriage and throughout her life Margaret Melissa listed her name as Murshon.

What happened to Mary and Kate (Annie?)? I have been unable to locate marriage records for these two daughters in Platte and Clinton Counties, MO.