Trains.fyi is a real-time map of train in the U.S. and Canada.
This project amalgamates data from train GPS tracking and displays all trains on one map.
Data is updated every minute, and the map updates automatically. This project was created by @rydercalmdown.
The map doesn't include many cities' local light rail. That notwithstanding, it's always nice to be reminded that passenger trains in the U.S. are largely one-a-day Amtrak services!