The class of the D Chicago & North Western was one of the first Atlantics with a wide firebox. With this arrangement, it was quickly discovered that firing was much easier and that much power could even be delivered with inferior coal. Production consisted of a first variant, of which 77 were built between 1900 and 1907, and another, of which 14 were built in 1908.

The first variant had an inside Stephenson valve gear with valves that were also inside the frame. The last ten of the second variant were built with a Walschaert valve gear and Young rotary valves.

The locomotives pulled trains, usually consisting of ten, sometimes eleven cars. 74 were later retrofitted with a superheater. When the wooden cars were replaced with steel cars and more powerful express locomotives were introduced, the class D was used in commuter and local traffic. Almost all locomotives survived into the late 1930s, 15 even survived into the late 1940s.