List of United States rapid transit systems by ridership

The following is a list of all heavy rail rapid transit systems in the United States. It does not include statistics for bus or light rail systems (see: List of United States light rail systems by ridership for the latter). All ridership figures represent "unlinked" passenger trips (i.e. line transfers on multi-line systems register as separate trips). The data are provided by the American Public Transportation Association's Ridership Reports.

...
Wikipedia