Canadian National class N-4 was a class of steam locomotives. These locomotives were built for the Grand Trunk Railway (GT) from 1906 until GT began purchasing class M freight locomotives in 1913. Initially classed D2 by the Grand Trunk, they were built as Richmond compound locomotives with boilers feeding and by cylinders.
The Grand Trunk started to rebuild and reclassify them; superheated compounds became class D3; those rebuilt with simple expansion cylinders and Stephenson valve gear became classes D4, D5 and D6. The D4 was extinct by the 1923 takeover of the Grand Trunk by Canadian National Railway; CN reclassified the others as N-4-a and N-4-b respectively. Some locomotives received Walschaerts valve gear and were classified D7 (N-4-d and N-4-e) and D9 (N-4-c); two received Young valve gear and were classified D11 (N-4-f). All simpled locomotives had their boiler pressure reduced to
Both GT and CN took some of these rebuilding efforts out of their original numerical sequence. CN numbered class N-4-a locomotives from 2525 through 2660 and numbered the alternative rebuilding classes from 2661 through 2686. The rebuilt simplified locomotives remained in freight service until the final replacement of steam with diesel locomotives.
Three N-4-a class locomotives have been preserved: