MARC runs 58 Penn Line trains during a normal weekday. A majority of these trains (39 each day) operate along a stretch between in Washington and in Baltimore. An additional 5 trains originate/terminate between Union Station and , while 11 trains run along the entire corridor between Union Station and Perryville. A single morning train and a single evening train run between Perryville and Penn Station, and a single early morning train runs from Martin State Airport to Penn Station. Unlike MARC's other two lines, the Penn Line operates all throughout the day and well into the night.