The classifications given by railroads to their steam locomotive fleets were as varied as the machines themselves with several different designations within a particular class! Canadian National Railway steam locomotives were no different and featured everything from small switchers to large 4-8-4 Northerns and 2-10-2 Santa Fes. The information here is merely meant to list these classes and does not go into detail about their specific differences among general types (i.e., Pacifics, Mikados, Prairies, etc.).
Because the CN operated all over Canada it used a wide variety of steam types from small Consolidations to, again, large Northerns and Santa Fes. Thankfully, for preservation's sake, no less than fifteen CN steamers survive today, in no small part thanks to the railroad itself who for years operated a heritage steam program. Some of the surviving types including Pacifics and Hudsons with five still operational. For a list of preserved CN steam locomotives please click here.
Class J
The CN's Class J included its fleet of 4-6-2 Pacifics.
Class K
The CN's Class K included a roster of Pacifics as well as 4-6-4 Hudsons.
Class N-5-d
This CN class of steam locomotives included its roster of 2-8-0 Consolidations.
Class O
The CN's Class O included its fleet of 0-6-0 switchers.
Class P
The CN's Class P included its fleet of 0-8-0 switchers.
Class S
The CN's Class S included its fleet of 2-8-2 Mikados ranging from Class S-1 to S-4.
Class T
The CN's Class T included its fleet of 2-10-2 Santa Fes ranging from Class T-1 to T-4.
Class U
The CN's Class U included its fleet of 4-8-2 Mountains and 4-8-4 Northerns ranging from Class U-1 to U-4.
Class X-10-a
The CN's Class X-10-a included its roster of 4-6-4Ts.
For more information on the steam locomotives like those operated by the Canadian National Railway consider Guide to North American Steam Locomotives by author George Drury, which includes nearly 500 pages of information on virtually all of the steam locomotive wheel arrangements and designs (including streamlined steamers) ever developed. The book is a great resource on steam locomotives and a fine reference tool; you should find it very useful.
Also, consider the book American Steam Locomotives from author Brian Solomon. While this publication does not include quite as much technical data as Guide to North American Steam Locomotives it is still a very good resource with lots of information and best of all, is loaded with photographs! If you're interested in perhaps purchasing these books please visit The Railroad Diamond by clicking the tab in the menu to your left marked "TRD Store".