Built by Baldwin in 1916 as No. 20 of the Oneida & Western short line in Tennessee, this 2-8-0 was sold in 1937 to the Rahway Valley Railroad of New Jersey where it operated until 1953. In 1959 F. Nelson Blount acquired it for his Steamtown operation, which for a time ran excursions over former Boston & Maine trackage between Keene and North Walpole, New Hampshire under the name Monadnock Northern (from the famous Mount Monadnock, near Keene). During a weekend commute between Boston, where I was attending Boston University School of Theology, and my student pastorate at North Charlestown, New Hampshire, I encountered No. 15 at Keene, probably in the fall of 1962. With 50-inch drivers and 20x26-inch cylinders, the engine sustained a boiler pressure of 200 p.s.i. and developed 35,360 pounds of tractive effort.

Oneida & Western No. 20 originally had slide valves, but was rebuilt by Baldwin with piston valves in a rare outside-admission arrangement — notice the two pipes, instead of the usual central pipe, extending from the top of the valve chamber. After being acquired by Steamtown the locomotive operated for five years. Currently it is stored inoperable at the Steamtown National Historic Site, its appearance altered by installation of a new headlight centered on the smokebox. No. 15 appears briefly in the Green Frog video The Boston and Maine.