Built by the American Locomotive Company (Alco) the low-hood S-2 was introduced in 1940 to replace Alco?s earlier high-hood switchers. The 1000 horsepower S-2 was a turbocharged version of the S-1. There were 1,502 S-2?s sold to North American Railroads.

Alco introduced the S-4 in 1950. The S-4 like the earlier S-2 was a 1000 horsepower switcher. Some 636 S-4?s were built for North American railroads.

The primary quick spotting difference between the S-1/S-2 and the S-3/S-4 can be seen in the trucks. The S-1/S-2 has Blunt trucks, while the S-3/S-4 has AAR-style trucks.

The versatility of the S-2?s and S-4?s were evidenced by their service in mainline railroads, shortlines, and industrials.

Atlas' version is back in service with handsome new paint schemes for modeler enjoyment.

Features Include:

- 5-pole skewed armature motor for reliable operation
- Dual-flywheels for maximum performance at all speeds
- Extra-thin handrails
- Factory-equipped with AccuMate? knuckle couplers
- Exceptional painting and printing
- Sturdy die-cast mainframe and gear cases