I read this correspondance with some interest. My gr grandmother was Mary Jane St. Louis. She was born about 1840 and lived in Belleville, Ontario when she was married. She may have been born in Belleville, I don't know. She and her husband lived for a while in Stoco, Ontario, and moved to Minnesota in 1877.
Is there possibly a relation between here and the St. Louis family you refer to?
I have a picture of her as well, but taken sometime after 1900. She died in 1917.