The approximately 3000 slate-roofed buildings identified by the Canadian Inventory of Historic Building computer program confirm the historic profile of slate roofing as a 19th-century urban phenomenon. In the absence of historic marketing data, the inventory data also provide the best impression of the geographic distribution of slate roofing that we have found. Fewer than 60 slated buildings were recorded west of the Ontario border, a factor consistent with a region whose urban growth occurred after the heyday of slate. Nearly four times as many slate-roofed buildings were recorded in Ontario than in Quebec, while Newfoundland showed more than the other three Atlantic provinces combined. In Quebec, buildings with slate roofs appeared principally in Montreal and towns of the Eastern Townships such as Stanbridge, Richmond, Sutton and Danville. Samples in Quebec were conspicuously absent. Half the slate roofs in Ontario were recorded by roofers Toronto, the roughly 1000 structures there providing the largest concentrated sampling in the country. Sizable groupings also appeared in London and Brantford. In Newfoundland, slating was confined to St. John’s and the Smith Sound area of the Avalon Peninsula.