The 4-4-0 or "American" type locomotive was widely used in North America
during the 1800's. This wheel arrangement was well suited to the grades and
curvature of the railroad of that time. Around 25,000 4-4-0 locomotives
were built by companies including Rogers, Baldwin, Cooke and Mason.
However, the design required the firebox to fit between the driving wheels
which limited its firing (and thus steaming) capacity and by 1900 larger
locomotives were needed.