The MARC (Maryland Area Regional Commuter) Train Service is a commuter rail system whose service areas include Harford County, Maryland; Baltimore City; Washington D.C.; Brunswick, Maryland; Frederick, Maryland and Martinsburg, West Virginia.

Penn Line: The Penn Line of the MARC Train Service operates primarily between Baltimore’s Penn Station, through BWI Thurgood Marshall Airport Train Station, and Union Station in Washington, D. C. Stops include Baltimore City, Odenton, and Bowie State University. In addition, there are 4 stops north of Penn Station [Martins Airport, Edgewood, Aberdeen, and Perryville] located in Harford County, Maryland.

Brunswick Line: The Brunswick Line operates between Brunswick, Maryland and Washington Union Station. This line also includes an extension to Frederick, Maryland and Martinsburg, West Virginia. Stops along the Brunswick Line include areas surrounding Washington D. C. such as Gaithersburg, Rockville, and Silver Spring, Maryland.

Camden Line: The Camden Line operates out of Camden Yards in Downtown Baltimore City and travels to Union Station in Washington D.C. Stops include Dorsey, Laurel, and College Park, Maryland.