Plum Island is an absolute gem located off the Northeastern corner of Massachusetts. This route runs the length of it north to south and back. Starting at the northern tip of the island, you’ll run through lovely residential beach neighborhoods along Northern Boulevard. You’ll turn right on the main drag - Plum Island Boulevard - to make your way over to the western side of the island, Turn left on Sunset Drive which will lead you to the entrance of Parker River National Wildlife Refuge. (There is a $2 entry fee for runners and bikers.)