I've decided the best way to plan a wedding in a park is to stalk the DNR website. What did I find? Rocky Gap State Park, with it's amphitheater.
Perfect for a low-key camping wedding and a TTD photo session in canoes. But its in Cumberland - a little out of the way. Plus, I'm not sure if we can pull off a camping wedding.
Enter Fair Hill NRMA. I'm still trying to figure out what this is, but their newly constructed visitor center is available for weddings. Only an hour from Baltimore - and near 95 and PA/Delaware - but I have no idea what it is! It seems to be a preserve, and according to Flickr, it is beautiful and involves covered bridges.