W1 (later reclassified to DH1) was originally delivered to Queensland Railways as a demonstrator unit. Built by Walkers Limited at Maryborough (Qld) in 1966, this unit wes deemed successful and purchased by QR in 1968. More locomotives were ordered between 1966 and 1974, with the class eventually numbering 73 units. Powered by Caterpiller engines, a notable feature of the DH Class were the slow speed controls to assist with shunting and other slow movements.

As trains became heavier and yards became fewer in number, the need for low-powered shunting units declined, resulting in the majority of the class being withdrawn from government service by the early 1990s. This would not be the end of their careers however, with most of the DH Class onsold to private concerns, including fifteen being sold overseas.

Two locomotives (DH32 and DH55) were sold to Relk Corporation (Malaysia) and converted to 1000mm gauge prior to being shipped. Thirteen DH Class were also sold to Vietnam Railways between 1993 and 1995.

One class member was sold to Mt Isa Mining and renumbered as 5804. It is included here for completeness.

Six of the class were sold to Cooks Construction in Dandenon (Victoria), with four reclassified as CC Class for use on brown coal trains between Yallourn and Morwell. All six locomotives were eventually returned to Queensland and sold to sugar mills.

The majority of the class have been rebuilt for use on various sugar cane networks in far north Queensland (see individual entries).

A number of the class have been preserved by various groups around Australia, including two operational units at Puffing Billy Railway - see DH Class (PBR) below for more information.