The Willamette locomotive was a geared locomotive of the Shay type, built by the Willamette Iron and Steel Works of Portland, Oregon. Key patents on the Shay locomotive had expired, and it was now possible for other manufacturers to produce Shay 'clones'.

Why would a small manufacturer not hitherto particularly well known for its locomotives pit itself against the mighty Lima Locomotive Works, top dog in the field of geared mining, logging and industrial locomotives? The answer was, simply, that Lima had, like many dominant companies, allowed itself to become set in its ways and unresponsive to customer demand.

The customers in question were West Coast logging companies, who wanted up-to-date and powerful locomotives and found Lima uninterested in updating their designs. The Willamette locomotives came with features that they were demanding, including the following:

  • Piston valves instead of slide valves on superheated locomotives. Slide valves, fine on a saturated steam locomotive, did not work so well when superheat was applied; the drier, hotter steam did not allow moisture to accumulate on the valve slides, which the design really needed to provide adequate lubrication. This fact was readily accepted by the customers and builders of road locomotives for regular railroads, and thus few locomotives with slide valves were produced after superheat became standard. For some reason, probably cost of retooling and redesigning, Lima refused to accept this change in the Shay design, and superheated Shays continued to have slide valves, causing in their customers' opinion many mechanical problems.
  • Walschaerts valve gear instead of Stephenson valve gear. Walschaerts' design was generally accepted as superior by builders of modern road locomotives, for simplicity as well as arguably better valve events, but Lima never adopted it in Shays except for a few examples.
  • Valve chests turned outwards. On Lima-built Shays, the valve chests on the front two cylinders faced forwards, and the one on the back cylinder faced aft. This made them hard to work on; the middle cylinder's was pressed tight against the foremost cylinder, and the front and back cylinders' valve chests were partially obscured by the running board and sheet-metal shrouds covering the cylinder area. The Willamette design made the valve chest area much easier to work on.
  • Cylinders clear of cab. All Shays had the aft cylinder impinging on the area of the cab, requiring the cab to be cut away and shorter on that side. The Willamette design had the cylinders moved clear of the cab area -- this redesign was helped by the reduction in the longitudinal space taken by the cylinders, thanks to the outward facing valve chests.
  • Revised truck springing. The Willamette design, while similar to the Lima Shay, had the springs inclined towards the center of the bolster, reducing lateral sway and improving the ride.
  • Higher-quality boilers. The Willamette company was a boiler-maker before its entry into the locomotive field, and it produced higher quality boilers for its locomotives than those available on Lima Shays, that leaked less steam.
  • Increased power and efficiencyThanks to the above improvements and many others in detail design, Willamette locomotives were reputed to be much the better of Lima Shays of comparable size. One comparison that has survived shows a Willamette hauling a slightly heavier load than an equivalent Shay while consuming 40% less fuel.

Three sizes of Willamette locomotive were produced; a 50 ton two truck model, a 70 ton three truck model, and a 75 ton three truck model.

It took Lima five years to come out with a Shay model that incorporated some of the demands of West Coast loggers, the Pacific Coast Shay, which had piston valves, better boilers, better truck springing, increased efficiency and other features. The valve chest positioning was never changed, nor was the impingement on the cab area of the aft cylinder. Both of the other major builders of geared locomotives produced improved models too; Heisler produced the West Coast Special Heisler, and Climax produced improved models though they had no special designation for them.

In all, thirty-three Willamettes were produced during a production run of eight years, from 1922 to 1928 -- very few compared to Lima's production, but the impact of the Willamette can be seen in practically every Shay built after that point.

All but one Willamette burned oil, despite their working for logging companies; oil burners produced only few sparks, and were less likely to set the forest ablaze in costly fashion. The only coal fired Willamette worked for Anaconda Copper.

Six Willamettes survive; none are in working order although several are undergoing restoration.

Fact checking and some details from the Geared Steam Locomotive Works,