The diesel engine, invented by Rudolph Diesel in the 1890s, was first used in a diesel-electric locomotive in the US in 1924. Samuel Hungerford, CNR president in 1934, and C.E.Brooks, CNR Chief of Motive Power, developed the first practical oil electric locomotive engine. It made its historic first run from Montreal to Toronto on September 26, 1929.

The 9000 was the first working internal combustion railway engine. Fuel oil drove an electric generator which turned traction motors, which then turned the wheels. It was more reliable, cleaner, cheaper and more efficient than the coal and steam train.
This technology signaled the end of the era of steam driven locomotives; by 1960 CN and CP used only diesel engines.