Canada is on the same numbering plan as the United States, and has the same habit of stacking codes rather than splitting them: Toronto answers to three, Montréal to six. Almost all of them serve a belt along the southern border, so that belt is drawn again below, at a size you can read.
How to read the map. Each patch is a province or territory, and the dots are the codes, pinned at the place the article names first. Where several codes cover the same ground — an overlay, which is how Canada has added numbers since the 1990s — they share one dot and are written together, so Toronto reads 416·437·647 rather than three dots stacked on each other. A split is different and stays apart: 250 is British Columbia minus the Vancouver that kept 604, so Victoria gets a dot of its own.
Where a patch is more than one province. Two patches are not provinces, because the codes are not. 902 and 782 serve Nova Scotia and Prince Edward Island together, and 867 is a single code for Yukon, the Northwest Territories and Nunavut — two fifths of the country's land area on one area code, and about a hundred thousand people. Drawing a border inside a shared code would invent a distinction the numbering plan does not make, so those provinces are drawn as the one area they dial as.
What a dot is, and is not. A code is pinned at the town its description names first, not at a boundary. Published area-code boundaries for Canada are not free to redistribute, so this map answers "which code is dialled around here" and does not claim to draw the edges. Codes the CRTC has set aside for future relief but not scheduled — 273, 460, 487, 537, 568, 851 and 871 — are in the plan but not on the map, because nothing dials them yet.
Sources. Code list: Wikipedia, List of North American Numbering Plan area codes, the same table the United States page is built from. Code locations: the coordinates on each town's own Wikipedia article, accepted only where the point falls inside the province the code belongs to. Geometry: Natural Earth admin-1 states and provinces at 1:50m, public domain, dissolved by dialling area and by region.