Left: General LeRoy Stone's Centennial Monorail of 1876. This stereo photograph is the only known image of the Centennial Monorail, a double-decker design driven by a rotary steam engine. It was operated as a novelty at the Centennial Exposition Picture kindly provided by Robert M Vogel.

General LeRoy Stone's steam monorail first appeared at the Centennial Exposition marking the USA's 100th anniversary in 1876. An elevated track extending about 170 yards was built in Fairmont Park in Pennsylvania. It connected the Horticultural Hall with the Agricultural Hall, and appears to have been called "The Saddleback Railroad".

The elaborately decorated double-decker vehicle had two main wheels; the rear wheel was driven by a rotary steam engine of the La France type. By this date it must have been clear that rotary steam engines were inefficient, but this monorail was more of a fairground attraction than a demonstration of exemplary thermodynamics. The LaFrance Manufacturing Company of Elmira, NY had been in business for just three years, and the LaFrance brothers had met Stone's needs by adapting the rotary force-pump used for their steam fire engines.

This design clearly solves The Monorail Problem (ie how to avoid falling off the rail) by means of the guide rails visible at the level of the front steps. The square structure at the rear is the driver's cab, with a short funnel protruding, and smoke and steam visible.

Some drawings of this monorail locomotive have now been discovered, in Edward Knight's Mechanical Dictionary. (Supplementary Volume 1884) For some unknown reason Knight makes no reference to General Stone or the Centennial Exposition, but simply describes it as a "single rail railway", without naming the inventor. However, there can't have been that many rococo-style monorails running around America at the time, so I am pretty sure it is the same machine.

Left: The Monorail crossing the ravine This shows the front of the locomotive, crossing the Belmont Dell ravine in the exhibition grounds. Note the short horizontal boiler. There was no provision for reversing and the locomotive had to be able to travel in both directions, like a tank engine.

Left: Knight's Monorail drawing. This drawing combines a front view, on the left, with a section of the passenger compartments on the right; seating was on two levels. The double-flanged vertical wheel on the bearing rail A takes the weight while the two double-flanged horizontal wheels D run on the side rails B to give stability. The side rails were 4ft 5in below the bearing rail. From Knight's American Mechanical Dictionary, Supplementary Volume 1884.

Left: Knight's Monorail drawing This shows the rear of the vehicle, with the boiler, rotary engine, and square driver's cabin. The La France type rotary engine is at the left, driving the vertical wheel C directly. The driving wheels were of 28in diameter. The boiler was of the locomotive type, 12ft long and 34in in diameter. Water tanks can be seen at E, with coal heaped in front of them. From Knight's American Mechanical Dictionary, Supplementary Volume 1884.

A modified version of LeRoy Stone’s design was used on a four-mile line between Bradford and Gilmore, Pennsylvania.
See The Bradford Monorail.

Left: Portrait of Roy Stone: 1864 Roy Stone was orginally a lumber operator from western New York State and Pennsylvania. In the US Civil War he reached the brevet rank of brigadier-general (Volunteers) as a leader of the 13th Pennsylvania Reserve Regiment "The Bucktails" He was born on 17 October 1836, in Prattsburg, New York State, and died in August 1905 in New Jersey.

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