Bill and Marion,

Washinton, Union Station is 36 miles from the camp, and Baltimore, Penn Stateion is 40 miles. So depending on where Marion is coming from either station will work about the same. Obviously she would pick the quicker or cheaper itinerary that got her to either station.

Amtrak home page

Now if she's renting a car then Hertz partners with Amtrak just search for rental cars on the Amtrak page, and they have your car waiting at the station.

Of course if she's riding with a friend then Union station connects to the Washington Metro.   The BWI (Baltimore/Washington International Amtrak station connects to the airport obviously and rental cars are available there as well.

Hope this helps.
Chance