Mine was on a 30 day railpass in 2014. It was what inspired me to write my railpass thread.
I went from Spokane-> Chicago (Empire Builder)
Chicago -> New York (Lake Shoe Express) (Stayed with a friend four days in NYC)
New York -> Boston (NEC)
Boston -> Portland, Maine (on a bus) (stayed with a friend a few days there)
Portland, Maine -> Boston (back on the bus)
Boston -> Washington, DC (NEC overnight)
Washington, DC -> New Orleans (Crescent) (stayed in a hotel for a night, my only hotel stay)
New Orleans -> Chicago (City of New Orleans)
Chicago -> Dallas (Texas Eagle)
Dallas -> Denton, Texas (Commuter rail), stayed with a friend for the weekend
Denton -> Dallas (Commuter rail)
Dallas -> Springfield, Illinois (Texas Eagle)
Springfield -> Galesburg (literally in a van, which, as I mentioned on my railpass thread, counted equally as a railpass segment)
Galesburg -> Emeryville, California (California Zephyr)
Emeryville -> Portland, Oregon (Coast Starlight) (stayed with a friend for a few days)
Portland, Oregon -> Whitefish, Montana (Empire Builder)
Whitefish -> Missoula, Salish Tribal Shuttle bus
Missoula, Hamilton -> Vanpool
I think I saw an incredibly great cross-section of the country in this time. Some of the places I stayed were because I knew people there (Portland, Maine and Denton, Texas are not exactly the must-sees of US tourism), but I feel that I had just as good of an experience there as I would have had in more "name" locations. When travelling by train like this, sometimes it is the smaller things that feel more important...I didn't see the Grand Canyon on this trip, but I had an egg salad sandwich in a diner in Galesburg! The American experience doesn't need to be "The American experience"
I saw 38 states in that 30 days (I believe), and it makes me wonder why people act live travelling and seeing the country is so difficult. Okay, not everyone can spend 30 days on a train, with half of those spent sleeping in train seats, so something this extensive isn't for everyone, but... the whole trip cost me a little over a 1000 dollars, counting all my expenses. Seeing the entire United States and having an opportunity to learn so much, really only cost as much as a piece of high-end consumer electronics or a month or so of car ownership. It was a once-in-a-life time experience, for a price that was not terribly high.
I want to do the same thing again...I made a spreadsheet to see 49 states using a 45 day Amtrak pass. I might actually get around to doing it, some day.