Introduced in early 1956, Alco's RS11 locomotive (catalogued as the DL-701), was powered by an 1,800-horsepower turbocharged V-12 version of Alco's 251B prime mover. The RS11 rode on B-B trucks of similar design to those used under the earlier RS3 and FA series locomotives.
Its hood style carbody featured notched corners that included the corner number boards and, on most units, sand filler hatches as well. These notched corners distinguished them from their Canadian RS18 cousins and made the RS11 an instant design classic.
Many roads purchased RS11s with a total of around 462 units produced. The largest customer was the Norfolk & Western with 99 units. However, the Pennsylvania RR signed on for 38 units, while the Nickel Plate took 35 and SP took 34. Other customers included the Delaware & Hudson, Duluth Winnipeg & Pacific, Lehigh Valley, Missouri Pacific, New Haven, Northern Pacific and the Seaboard Air Line.
One of the most reliable of Alco locomotives, RS11s survived in Class 1 usage well into the late 1970s and several are still in use on short lines today.