Myrna, I hope you are still searching for your roots and will see this post.
I am also searching for this family line. I am related to the William H. Johnston in your post. I received a death certificate for William H. Johnston, born 11 Feb. 1845 and died 6 July 1920 in Olympia, Washington. I know this is my relative because he is buried next to my Grandmother. His death certificate has his name as William H. Johnstone. It list his parents as James Johnstone, born at sea and Ann Yocome, born in Canada. (I know spelling is off, it is what is on certificate.) The information was provided by a Katie McEwen.
If you have information on James and Mary Ann Yocum Johnston of Canada I would appreciate any help you can give me.
Thank you, CarolynDMC670@aol.com