The Mt. Washington Cog Railway is the oldest such railroad in the world, opened on July 3, 1869. It climbs from an elevation of 2700 feet to just below the 6,288-foot summit of Mt. Washington, with an average gradient of 25% and a ruling grade of 37.41%. Until 2008 it was entirely steam-powered. In that year the first of several diesel-hydraulic locomotives was built. Today only the first trip of each day is steam-powered.

As with all rack railways, the running rails are used only to support the train. Propulsion is via a pinion gear that meshes with the central rack rail. The Cog uses the Marsh rack system, named after its inventor and founder of the Cog, Sylvester Marsh.

The first time I rose the Cog was in 1989, when I was four. I remember little of that trip, except that the weather at the summit was quite poor and I was scared I'd be blown off the mountain by the wind. On my second and third trips, which the pictures below are from, the weather at the summit was as clear as it was at the base station, albeit colder.