I wonder why Amtrak is not serving Yellowstone Park?
It's a great tourist attraction and it's very far from major airports.
The only way to get there - driving VERY long road.
Amtrak could attract many tourists like they did it with Glacier National Park.
Unfortunately, Yellowstone is closer to major Interstates (I-90 and I-15) than it is to any Amtrak service (the Empire Builder or the California Zephyr). The only way that Amtrak could provide any kind of service to Yellowstone at this time is through bus service from the Builder or Zephyr as there are no rail connections near Yellowstone. At one time, both the Union Pacific and the Northern Pacific had tracks that ran to the edge of Yellowstone (UP to West Yellowstone, MT; NP to Gardiner, MT), but both were abandoned and removed many years ago.
The best Amtrak could do, short of rebuilding one of the branches to Yellowstone, is to resurrect the North Coast Hiawatha along the former NP (now BNSF and Montana Rail Link) and provide a bus link at Livingston, MT. Personally, I'd love to see the NP branch rebuilt to Livingston, and Amtrak run through cars from both Seattle and Chicago to Yellowstone, but that's not likely to happen any time soon.