The R class engines of 1897 had not proved appropriate for the steep gradients made necessary by the crossing of the Darling Scarp, due to their lack of power.

In 1900, orders were placed with British manufacturers, Nasmyth, Wilson & Co and Vulcan Foundry for forty-five 4-6-2 locomotives.

[1][2][3] Due to slow delivery times by the British companies as a result of full-order books and a preference for larger orders, twenty modified E class locomotives were ordered from the Baldwin Locomotive Works, Philadelphia and became the WAGR Ec class.

The E class eventually totalled 65, with 15 examples being built by Nasmyth, Wilson, 30 by Vulcan Foundry and 20 by North British.

The first fifteen entered service in 1903/04 and were successful from the outset, providing a much needed boost to WAGR locomotive power.