ALCO HH series

The ALCO HH series was a family of early diesel switcher locomotives built by the American Locomotive Company in Schenectady, New York, between 1931 and 1940. They were ALCO's first diesel switchers in true series production and among the first land vehicles anywhere to use diesel-electric power transmission. The name stands for High Hood. After a prototype sold to the New Haven as number 0900, four production models followed: the HH600, HH660, HH900 and HH1000, named for their rated horsepower, using McIntosh and Seymour six-cylinder engines. A total of 177 were produced before the S series replaced them in 1940, and a few survive in revenue service and in museums.