I might do this first from my home state. Cargohop and see where I end up. I could end up in California or Texas or Utah, or maybe not even in the US. The mystery is the fun part.
Careful on trains, one wrong step while the train is moving and you'll be sucked under the train and end up on a gore website. Also, Union Pacific is super strict when it comes to train hoppers and they will call the police who will be waiting for you once the train stops. Good luck!
if hobos can do it so can I. Earplugs are cheap
Can't speak for BNSF but Union Pacific locks empty train cars and you have to see where the cars are coming from because 10 times out of 20 the empty cars go out east to the midwest to get refilled with grain. Boxcars are usually filled with things like pallets, beverages, etc., at a hub near a port. I think they do it mainly in California but I am not too sure as UP has a ton of hubs near ports.