From Boston: Take Route 95 North to Portsmouth, New Hampshire. Go left at the split (Exit 4), which will put you on the Spaulding Turnpike (Route 16 North) toward New Hampshire. Follow the Spaulding Turnpike to Exit 16 and follow the signs to Route 125 North toward Milton. Go one block and take your first right onto Flat Rock Bridge Road. At the stop sign, cross Salmon Falls Road and continue driving straight over the bridge to the campground entrance.