The NW2 was the successor of the Winton-engined switchers that featured the new EMD 567-series engine. It was introduced in 1939 and although the N in the designation stood for “Nine hundred horsepower”, it had in fact 1,000 hp. The W stood for a welded frame, but at this point no new C model with a cast frame was introduced. By 1949, a total of 1,145 had been built of the standard NW2. The three largest customers were Union Pacific with 95, Indiana Harbor Belt with 78 and Southern Railway with 69.

Cow-calf pairs with only one cab in total were designated TR. After only three pairs of the original TR, 36 were built of the largely similar TR2. Three cow-calf-calf sets were built as TR3. As a variant of the NW2, Great Northern had ordered seven NW3 for passenger service. These had a longer frame to fit a larger cab and a steam generator in front of the cab. They were geared for 80 mph. Another passenger variant was the NW5 of which the Great Northern was again the main customer with ten out of 13 locomotives. This variant had a more modern 567B engine and the steam generator in a rear short hood.