The Indiana Harbor Belt Railroad is a Class III railroad in the United States. The line is comprised of of track—30 miles of single mainline track, of double main track and of additional yard and side track—starting northwest of Chicago in Franklin Park, Illinois, traveling southeast around the city to its headquarters in Hammond, Indiana. The line's largest yard, Blue Island, is located in Riverdale, Illinois with other yards in the Indiana cities of Hammond and East Chicago. The Gibson Yard, located in Hammond, is arguably the largest auto-switching operation in the United States.