It’s common knowledge that the Northeast Corridor is Amtrak’s best line, but the northeast is not the only place in the US where a lot of people ride intercity trains. This map by Michael Hicks shows that California, the area around Chicago, and the Pacific Northwest also stand out.
In the map, each circle represents one Amtrak station. The larger the circle, the more riders there are at that station.
Cross-posted at BeyondDC.