Really desiring to build bigger and more powerful locomotives the GWRs' finest locomotive engineer, George Jackson Churchward tested a number of inovative ideas, including French-built DeGlenn compound atlantics 4-4-2s. Churchwards designs set the template for the remainder of the GWRs' existance, lococomotives so far ahead of their time in the 1900s that the basic design was still considered state-of-th-art half a century later.
The County class 4-4-0 was built as a stop-gap locomotive, in 1904 Churchward wanted to build 4-6-0s, but other engineers were concerned about the size of these new locomotives. They should have been more worried about the County! Churchwards' answer was to use the powerful 2-cylinder engine designed for the Saint class 4-6-0, but a shorten the frame to the 4-4-0 arrangement. The result was a locomotive of immense power and a reputation for a rough ride as the drivers whipped 70+mph out of their new machines.
Being something of a stop-gap the 4-4-0 Countys were withdrawn early, replaced by the 4-6-0 locomotives originailly intended. The last of the 4-4-0 Countys was withdrawn in 1933, but the names were revived in the late 1940s for a new class of powerful 2-cylinder 4-6-0 locomotives designed by the GWRs' last chief engineer, F W Hawksworth.