Bradley Palmer
Bradley Palmer State Park map of the State park in the summer: - http://www.mass.gov/dcr/parks/trails/BradleyPalmer_summer.gif
This is a trail map, it's large, you can run your dog off leash, but you need to be careful of other dog owners, of horses and moody people. Mainly horses, people can get moody if your dog attacks their horse or barks or spooks it. They will surely tell the authorities. You should always have your leash on hand and be ready to call Mia back if she is off leash and be sure she will come to protect you and your pet. I'd hate to see your pet get hurt from a horse hoof.
Official site of Bradley Palmer State Park - http://www.mass.gov/dcr/parks/northeast/brad.htm
Google Map showing the Park - http://maps.google.com/maps?f=q&hl=en&q=bradley+palmer+state+park,+MA&sll=37.09024,-95.537109&sspn=49.223579,92.285156&ie=UTF8&z=14&ll=42.652016,-70.900612&spn=0.045009,0.090122&t=h&om=1