Despite the railroad 's incomplete state, the first paying customers started riding on August 14, 1868, and the construction reached the summit in July 1869. The early locomotives - represented today by the restored display locomotive, # 1 Old Peppersass - all had vertical boilers, like many stationary steam engines of the time; the boilers were mounted to the locomotives ' frames with twin trunnions, allowing them to pivot as the locomotive and coach climbed the grade, permitting gravity to always keep the boiler vertically oriented, no matter what the gradient of the track. Later designs introduced horizontal boilers, slanted so that they remain close to horizontal on the steeply graded track.
what powered the original locomotives on mount washington cog railway
steam engines