The class L-2 Hudsons of the Chesapeake & Ohio were 4-6-4 express locomotives introduced in 1942 to haul the fastest trains on level routes. They had to haul 15-car trains at 90 mph or 145 km/h. Trains on mountainous routes were already hauled by the “Greenbrier” 4-8-4 which had been introduced in 1935.

Their features included 78 inch (1,981 mm) drivers and a large 255 psi (17.6 bars) boiler with thermic syphons and an Elesco feed water heater. All axles of the locomotive and even the side rods had roller bearings. The Franklin type E booster was a special express variant that allowed operation up to 33 mph or 53 km/h.

The original class L-2 consisted of eight locomotives built in December 1941 and the following January. In 1948, five more of a revised design followed as L-2a. They had Franklin rotary cam poppet valves instead of piston valves and were the last steam express locomotives any US railroad purchased. After only a short career, they were scrapped in 1953.