Jake,
Again this may be too late, but if you are at Sandy Beach look to the left, waaaaay down the way & you will see Baltimore. Well, there's a light there and by process of elimination it has to be Baltimore. Baltimore area has bunch more if you have good map and some time. Last time I was there didn't have either.

If you go down the West shore of the Chesapeake you can do a one day loop from DC area that includes a number of lights - Cove Point, Drum Point, what's left of Cedar Point's lantern at Pax River NAS, Point Lookout, Point No Point way out in the water from the shore just before Point Lookout, Piney Point.

There is a nice little $6 book "Lighthouses of the Chesapeake" that shows all. My copy came from Calvert Marine Museum (Drum Point). Museum is quite nice.

Happy hunting,

Dave