I too am searching for Joseph Garrow (Garreau) who moved to Helena, Montana in, I believe, the 1880's. He was orginally from New York state, but may have been born in Canada. He was married to Hermine "Minnie" Shatraw (Chartrand). I do not know if they were married before or after he moved to Montana, but I do know that she also was from New York, probably via Canada. He died as a young man with four surviving children in Helena, Montana, I think about 1899.
If any of this information might relate to what you have I certainly will be most appreciative to hear from you. I have one photograph of him taken as a young man with his friend and brother-in-law Edward Emmanuel Shatraw.