Mary Clark is a mystery. She was born in approximately 1858 according to the 1871 census. She is not part of the family on the 1861 census, and is not seen again afterwards.

It may be thought that the name was written incorrectly, and that it really should be Samuel who is about the same age, but he is listed as being in Michigan on the 1870 census with his brother Oliver S Clark.

So Mary may have been adopted, or the daughter of a neighbor or relative, or perhaps even a grand-child.