The RS-1 was introduced by ALCO in March of 1941
with the delivery of the first of two units to the Rock Island.
Combining the accessibility of a switching locomotive and the
higher-speed tracking of a road unit, the RS-1 started a revolution
in locomotive design that was soon embraced by all of the major
diesel-electric builders. Despite ALCO's own introduction of higher
horsepower roadswitchers, the 1,000 h.p. RS-1 had a production span
of 19 years (1941-1960) with 623 units.