The DL10s were ordered in 1966 from Alco & MLW (4 from Alco, 6 from MLW) as replacements for most of the remaining class DL2 (RS-1) & DL3 (RS-2) locomotives. The railroad wanted some higher speed trucks (but not Hi-Ads) so all of these locomotives were delivered with lightweight GSC trucks.

In 2024, the fleet was expanded by one with the purchase of Alco’s last Schenectady-built unit. It is earmarked for (eventual) display at ILW’s Schenectady works, but is currently in service on the TdM