It is not easy to find consistent information on the subspecies of Canada geese, and their ranges.  But the ornithologists at Cornell have this fairly useful page, which gives information on Branta canadensis maxima, the giant Canada goose, consistent with what Gary Lantz wrote:

http://www.birds.cornell.edu/AllAboutBirds/BirdGuide/Cana ...

But David Allen Sibley refers to the Common Canada goose as "the largest and most widespread."  And the National Geographical Society's "Field Guide to the Birds of North America," Second Edition, with an apparently outdated range map showing no presence in southern Ontario and Quebec and the NE US, gives the names of four subspecies, none of which is B. c. maxima.  Similarly, Peterson refers to "the Atlantic race," and implies that that is the largest.

The Cornell page also supports Ivriniel's observation that Canada geese are found year-round in southern Canada.  One would need to distinguish whether the same individuals are year-round residents, or whether there is seasonal alternation of northern and southern populations.

I am grateful to Gary Lantz for commenting on the beauty of these animals, and on how it is not too difficult a problem to learn to co-exist with them.

According to the Canadian Wildlife Service's Hinterland Who's Who on Canada Geese there's dispute about how the various races of Canada Geese should be organized but this is what the CWS has to say about the Giant Canada Goose:

One race, the Giant Canada Goose, used to breed in southern Canada and the northern United States but disappeared from most of its range by the late 1800s. Early settlers may have gathered Giant Canada Goose eggs and rounded up and slaughtered many of the geese during the flightless moulting period. Beginning in the early 1900s, Canada Geese from captive breeding flocks were reintroduced into the southern parts of their former range. This practice continued through much of the 20th century, and Canada Geese were eventually restored in Pennsylvania, New York, Ontario, and west to southern Alberta. During this period, geese were also introduced to areas where they may not have bred before.

These reintroduced populations have since exploded, and Canada Geese have become a nuisance in many areas. The birds thrive under the close protection and feeding opportunities they find in parks, near suburban wetlands, and on lawns or golf courses. Because no hunting takes place in these areas, there are few natural factors working to limit population growth and disperse the birds. Populations of urban Canada Geese are still growing, and the range of these birds is still expanding. Problems associated with geese include droppings on lawns and beaches, which may contaminate drinking water sources, aggressive behaviour toward humans, and collisions with aircraft. Wildlife managers are increasingly being asked to balance the careful conservation of some types of Canada Geese with programs designed to limit or reduce populations coming into conflict with agriculture or other human activities. To deal with problem geese, the Canadian Wildlife Service has liberalized hunting regulations as much as possible. It has also allowed other management options under permit.

http://www.hww.ca/hww2.asp?id=35

In any case, according to Wikipedia the American Ornithological Union reorganized the subspecies of Canada Geese in July of 2004. Maybe your bird books predate that?

Ivriniel