Initially classified as "A" class by the Victorian Railways, the nA Class were built by Baldwin Locomotive Works in the USA and Victorian Railways' Newport workshops to haul trains over the 2'6" narrow gauge lines owned by VR. The first two locomotives, 1A and 2A were manufactured in the USA and assembled at Newport Workshops, with the remaining 13 class members manufactured and assembled at Newport with the final locomotive, 17A delivered in 1915. 

Confusion between the narrow gauge A class and the broad gauge A, AA and A2 classes lead to the "n" prefix being applied to the narrow gauge units, creating the nA class. 

1A was built as a simple cylinder locomotive while 2A was built as a compound cylinder locomotive. The remaining members were built with simple cylinders.

By the mid-1920s these small locomotives were not able to handle the increasing traffic on the Moe-Walhalla and Colac-Beech Forest-Crowes lines, and two G Class Garratt locomotives were purchased to supplement the fleet.

The remaining class members are all preserved at Puffing Billy Railway in Belgrave, Melbourne. All survivors have been restored to operational condition except for 3A, which is under restoration to its as-built state with small water tanks and wire cowcatcher.