Several roads used the 2-8-8-4 configuration also commonly called the 'Yellowstone'. The Duluth, Missabe & Iron Range among them, but others as well, and one variation holds the tractive effort record for N. American steam. It is the Great Northern's R-2.
The SP just built 'em backwards. They're the first 'tunnel motors'. The SP had long tunnels, and those magnificent articulateds (the SP referred to them as 'Malleys'), burned a lot of fuel trudging through those tunnels. Lots of smoke, endangering the crews. By placing the stack rearward, cab forward, the crew could be sure of both better ventilation AND better vision. Win-win.
Note that the real spelling of 'Malley' is Mallet, after a Frenchman who designed and built the first dual-expansion steam locomotives. The Big Boy, Challenger, Yellowstone, Virginian/Allegheny, and Cab Forwards were not technically Mallets because the boiler supplied simple steam to all cylinders. A true Mallet uses simple steam once, in the rear cylinders usually, and then the expanded and cooler steam is ducted forward to the massive front 'low pressure' cylinders. Examples of those would be the Norfolk & Western's famous Y series. That road's Class A 2-6-6-4 is articulated, but it's like the Yellowstone and Cab Forward; simple steam in all four cylinders.
Yet another note: the Y6's had valves that allowed full steam to all four cylinders at startup, but them crafty engineers also added a 'booster' valve that allowed injection of simple steam into the front cylinders when the train was up in speed if it were needed.