These two locomotives were built by Baldwin for the New Haven in 1905 and 1907 as part of the G-4 class and were used by them until 1943. At that time, there were already significantly more powerful steam locomotives with a significantly higher axle load in the USA, and so the G-4 class examples that were still in use became superfluous. The Second World War brought with it the Lend-Lease Act, which was intended to strengthen the US allies by supplying war-related technical equipment. This also included the railways in order to be able to cope with the increased transport tasks.

In this environment, two locomotives were sold cheaply to the Commonwealth Railways and numbered CA78 and CA79 there. These were tender locomotives with a 4-6-0 wheel arrangement, which were suitable for mixed traffic with a coupling wheel diameter of 73 inches and had an axle load of around 45,000 pounds. The two locomotives were not technically identical, but differed in the area of valve gear. While the CA79, built in 1905, had Baker-type gear, the CA78 had Southern-type gear. The service life of the locos in Australia was very short as the newer engine was retired immediately after the end of the war and the other in 1950. Both were scrapped in 1956. A similar history was shared by the eight CN class locos used by the Montreal Locomotive in 1907 and 1908 Works and bought by the Canadian National in 1942.