The Penn Line is a MARC commuter rail service running from Union Station in Washington, D.C., to Perryville, Maryland, via Baltimore's Penn Station along the southern leg of the Northeast Corridor. It is MARC's busiest and only electric line. With trains running at speeds of up to , it is the fastest commuter line in the United States. The service is operated by Amtrak under contract to the Maryland Transit Administration. MARC sets the schedules, owns most of the stations, and controls fares, while Amtrak owns and maintains the right-of-way, supplies employees to operate trains, and maintains the rolling stock. It is by far the busiest of MARC's three lines, with twice as many trains and twice as many passengers as the Brunswick and Camden lines combined.