List of U.S. Class II railroads
In the United States, a Class II railroad, sometimes referred to as a regional railroad, is a railroad company that is not Class I, but still has a substantial amount of traffic or trackage (and is thus not a short line). The Association of American Railroads (AAR) has defined the lower bound as 350 miles (560 km) of track or $40 million in annual operating revenue.
Source: Wikipedia — List of U.S. Class II railroads (CC BY-SA 4.0)