The seventeen CL class locos  were introduced into service by the then Commonwealth Railways between 1970 and 1972 and were the first high horsepower units in the CR's fleet. 

The high horsepower (3000hp) concept was quite revolutionary for Australian railways of the time and further development led to the VR C class and the SRA 81 class, and led directly to the present time when high horsepower units are the norm. 

While nominally confined to the Trans Australian line hauling freight and passenger trains during the 1970s and '80s, they all ran load trials on the NSWR before delivery and participated in early experiments in "through running" to Lithgow in 1974. 

CL1 also spent considerable time in NSW in 1975 undergoing trials on the Main South to Albury, an activity that resulted in the ordering of the 81 class. 

By the early 1990s they were in need of attention and the entire class was converted to either CLF (for Freight) or CLP (Passenger) configuration, which involved a varying regime of internal and external changes, depending on class. 

The CLFs continued to perform long haul freight work on the extended standard gauge network, while the CLPs, fitted with passenger train specific refinements, such as head end power to operate the air-conditioning and other services of the passenger trains, quickly came to dominate the premier Australian National passenger trains, the Indian Pacific, Ghan and the Overland. 

As the '90s progressed and the great changes of that decade, such as Privatisation, began to take effect the CLPs lost their premier position as prestige passenger power and can now be found hauling freight for any number of operators in all parts of the Australia wide standard gauge network.

CL in AN Green and Yellow, from the Austrains collection