Significant numbers of Canadians emigrated to the US in the late 19th and early 20th centuries. In fact during the last three decades net migration to Canada was negative. Immigrants from Quebec went mostly to neighboring New England. New England also attracted many immigrants from the Maritimes; New England were referred to as the "Boston states." Detroit attracted many immigrants from southern Ontario.
US Census data separated the Canadian-born into Canada - French and Canada - Other (it isn't clear whether "French" meant born in Quebec or French-speaking). In 1900, there were 1,179,922 Canadian-born in the US, including 395,126 French Canadians and 784,796 English Canadians. That was the year in which the French Canadian-born population peaked, though the Canadian-born population increased until 1930.
In 1930, the population born in Canada and Newfoundland was 1,302,392, including 302,496 French, 678,442 Other and 23,971 from Newfoundland.
Here are the cities with the largest Canadian population (defined by Canadian and Newfoundland-born or at least one parent born there) and percentage of the population. Clearly Detroit and Boston (and adjacent Cambridge) - where they numbered over 100,000 and more than 10% of the population - were the main centers:
Detroit 175,658 11.2%
Boston/Cambridge 120,052 13.4%
New York 85,903 1.2%
Chicago 74,350 2.2%
Los Angeles 59,931 4.8%
Buffalo 36,006 6.2%
Seattle 33,011 9%
In all of these cities, most of the Canadian population was English-speaking. Boston likely had more Maritimers than Halifax at the time.
French Canadians represented a large percentage of the population in several New England mill towns, including Fall River (25,899, 22%), Lowell (22,180, 22%) and New Bedford (20,384, 18%).
