The DL23 class are an ILW rebuild – to C-636 specs – of a fistful of used C628s purchased from the Chicago & Northwestern after being retired from iron ore service. They served for many years on the D&H before electrification swept them off the system, and then they were scattered around various Parsons Vale routes that are still not electrified.

While they were serving on the D&H, most of them went through Colonie to have their high short hoods cut down; by the time the electrification was finished only 3 (680,688,700) still had their original N&W high nose.

In the mid 2010s (after 30 years of service for some of them) the Parsons Vale sent most of them off to ILW for another rebuilding; this time to “C-635"s with a Cummins QSK78 prime mover and all AC electricals. The C-635s are, despite having less horsepower, considerably more powerful engines than the C-628ms because their AC motors are much less prone to wheelslip. (Where 3 C-628ms were needed, 2 C-635s can do the job.)

As if 2024, all of these locomotives still operate.