The Northeast Corridor (NEC) is the busiest passenger rail line in the United States by ridership and service frequency. The route is fully electrified and serves a densely urbanized string of cities from Washington, D.C. in the south through Baltimore, Wilmington, Philadelphia, Trenton, Newark, New York, New Haven, and Providence to Boston. It also has branches connecting Philadelphia with Harrisburg, Pennsylvania; New Haven with Hartford, Connecticut and Springfield, Massachusetts; New York City with Albany, New York, and several other commuter destinations. The busiest passenger rail station in the United States is Pennsylvania Station in New York, the central hub of the Northeast Corridor.The NEC is immediately identified by the use of overhead wires and high speed rolling stock. Mostly operated and owned by Amtrak, the NEC offers the only true high-speed rail service in the United States, Amtrak's Acela Express. Several commuter rail agencies provide local service along the Northeast Corridor, some electrified and some diesel-powered. These rail networks include MARC in Maryland and Washington DC, SEPTA in Pennsylania and Delaware, NJ Transit in New Jersey, Metro-North in New York and Connecticut, Shore Line East in Connecticut, and MBTA in Massachusetts and Rhode Island.The Northeast Corridor mainline closely parallels Interstate 95 for its entire length.