It replaced the RS-10 in MLW's catalogue, and production totalled 351 locomotives, to eight customers.

It was the Canadian version of the ALCO RS-11, although MLW did manufacture the RS-11 for Ferrocarriles Nacionales de México.

Canadian National Railway, by far the largest buyer of the RS-18, continued to specify the long hood as the front.

The remaining production was for locomotives with a low short-hood, giving the train crew much better forward vision.

West Chester Railroad #1803 is an ALCO RS-18 built in 1960 by the MLW for the Canadian Pacific Railway and was numbered 8762.