Many people changed there name in Canada before coming to St. Lawrence Co.
My family was first in Quebec, as St. Onge's, Chatigny's, and Dupuis. They then went to Ontario and changed to Santos, Chateney, and Dupuy/Dupee, and when they came to Ogdensburg they became Santaus' and the Dupuis/Dupuy became Wells and the Chatigny's became Shatney's and to this day that is what we are.
Ontario had more German and English-speaking people then Quebec and that may have had alot to do with it.
I am not disputing that there were Santimaw's in Canada, I am just saying that for the most part you will find that the Santimaw family became Santimaw's in the mid-1800's, around the same time many French names were changed either in Ontario or NY/Vermont.
I do not personally know any Santimaw's in Ogdensburg but I have seen the name often in my research of Northern NY. I live in Western NY and we don't have any Santimaw's here as far as I know, although many French Canadians did settle here.