Compared to the Shay and Climax, the Heisler was a rather latecomer. In 1892 Charles L. Heisler received a patent on the locomotive that would also bear his name. Although superficially resembling a Climax, what set his locomotive apart was that the cylinders were slanted inwards at a 45 degree angle. The center shaft only drove one axle per truck, as the wheels in each truck were connected with a side rod.
In 1894, the Stearns Manufacturing Company (Erie, PA) began reorganizations,
and became the Heisler Locomotive Works in 1907. Just as with the Shay,
there were two and three truck models, with sizes up to 90 tons.
Heislers were made until 1941. There were 850 built, of which 32 still exist.