Dan,
We did the America By Rail videos as a series for the general public. The gist of each was to travel from point a to b, hopefully a scenic Amtrak route, and visit some side-trip railroads along the way.
We were short of side-trips for the above mentioned route, which started in San Diego and went to Seattle. We were early in the year(April), which eliminated some railroads.
The key factor of course was the Amtrak routes.
We did the Columbia Gorge which at the time had the PIONEER running and we got both trains within 15 minutes of each other from an overlook called Ruthton Point, near Hood River. Thats how we slid into the Mt. Hood Railroad segment!!
Another factor in all this was the times of Amtrak trains. We had to deal with reality here, and folks wanted us to do the Empire Builder too, but it was dark through the best portions of the route, and nobody would like that!!!
The point is Sumpter would be a stretch for the America By Rail series, but would be nice to visit for the railfan in me someday. You can be sure that we will make it a major part of any trip we make out that way in the future!
Greg