The ALCO S-2 is a diesel-electric locomotive built by the American Locomotive Company (ALCO) from 1940 to 1950. It features a 1,000 horsepower engine and is primarily used for switching and short-haul freight operations. The S-2 is known for its distinctive design, which includes a low hood and a short wheelbase, making it highly maneuverable in rail yards. With over 1,000 units produced, the ALCO S-2 became a popular choice for many railroads across the United States. Its reliability and ease of maintenance contributed to its long service life, and many units are still in use today, often found in industrial settings or preserved by rail enthusiasts.