Patent drawings for the Alco DL series locomotives - the DL-109 was Alco's first mass-produced cab unit, precedding the PA series by a number of years. Distinctive by their three-panel cab windows, the DL-109s were only bought in any significant numbers by the New Haven, although the C&NW, GM&O, Milwaukee Road, Rock Island, Santa Fe, and the Southern each had a few examples on their rosters. The NH used the DL-109s to meet a wartime traffic surge, and the locomotives were almost constantly in use, hauling passengers by day and freight at night.
