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 Perfecting the American Steam Locomotive by author J. Parker Lamb. As the name implies the book details the earliest history of steam engine technology, even before it was used in railroad applications. His book later explores the development of steam locomotive technology in the United States from the 19th through the 20th centuries, covering not only the most popular steam locomotive designs but also the most successful manufactures to build them. The book has received excellent reviews and 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 Lamb's book, Perfecting the American Steam Locomotive, 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 either (or both) of these books please visit the links below which will take you to ordering information through Amazon.com, the trusted online shopping network.