August 7, 1895
The Type of Coach Samuel Clemens traveled in.
That night, 7th, at 11:30 we went aboard the sleeper on the Great Northern Road.
Everything was in readiness for us.
The next day was one full of interest as we were to ride over the Rockies on the zigzag road.
Perhaps, the Great Northerns Engine 517
pulled  Twain's sleeping coach like this.

Local artist David Hose has painted a beautiful rendition of
Great Northern steam locomotive #2555 (a 4-8-4, S-1 class Northern)
on the side of a building in downtown Sultan, WA. 
This mural is definitely worth a look on your next visit to Stevens Pass. 
It is visible from US Highway 2 as you head west. 
Note the detail of David's work in the close up with him standing next to the cab of 2555.  October 2005 photos by Lindsay Korst.
Twain's train traveled over the FIRST TRACKS that Great Northern built. There was NO TUNNEL.
The first route over the pass was a series of switchbacks, with grades of up to 4 % on the West side and3.5%
on East side, was completed on January 6, 1893. 
To traverse a switchback thetrain has to travel to the end of the dead end spur,
then the switch is thrown and engine reversesdirection to go into next spur. 
This is repeated at each spur. 
The spurs were only 1000 feet long so themaximum  train length was 2 engines and 23 cars. 
With a heavy load and snow that could be reducedto as little as 5 cars. 1893-1925.
The two photos taken in the Cascades,
display that the engine could be a 2-4-0 like this.
BUT, GN records lead me to believe the 517 was a 2-6-0 Engine.

A Chicago and Alton Railroad Pullman car interior c1900.