The OR&N 197 was built by The Baldwin Locomotive Works in May, 1905 as the last of an order of four identical locomotives. Of the four (Union Pacific class P-2), the 197 is the only survivor. One similar UP locomotive, the 3206, still exists and is located in Spokane, Washington.
The OR&N was controlled by E.H. Harriman at the time, who was known for developing standardized designs for the equipment on his railroads. As a result, the 197 bears a strong resemblance to Southern Pacific locomotives of the same era, although the SP did not purchase any identical engines.
The 197 was originally built as a four-cylinder compound (double-expansion of the steam) locomotive with Stephenson valve gear, having the high pressure cylinders located between the frames. These high pressure cylinders drove the second driving axle which was of a crank design, similar to an automotive crankshaft. The low pressure cylinders received exhaust steam from the high pressure cylinders, and were located outside of the frames. These drove the second axle more conventionally, with external main rods driving crank pins on the driving wheels.
In a 1923 rebuilding at Union Pacific's Albina Shops in Portland, the engine received new cylinders, converting her to simple (single expansion) two cylinder operation. The valve gear was also converted from Stephenson to Walschaert, which was becoming common on modern locomotives.