Middle Ground Island is a small island located in the Parker River National Wildlife Refuge. The island is accessible by boat from the refuge's headquarters or Plum Island. The island is part of the refuge's wilderness area, which means that visitors must follow certain rules to protect the natural resources and wildlife. Some of these rules include: staying on designated trails, not disturbing or feeding wildlife, not collecting plants or shells, and carrying out all trash.

Located along the northeast coast of Massachusetts, Parker River National Wildlife Refuge was established in 1941 to provide a feeding, resting, and nesting habitat for migratory birds. Most commonly associated with Plum Island, a barrier beach island, the refuge is comprised of more than 4700 acres of diverse habitats including sandy beach and dune, cranberry bog, maritime forest and shrubland, and freshwater marsh. The most abundant habitat on the refuge is its 3,000+ acres of salt marsh, one of the most productive ecosystems in nature. Parker River provides a pristine coastal habitat for over 300 species of resident and migratory birds, as well as a large variety of mammals, insects, fish, reptiles, and amphibians. The refuge also provides critical habitat for the federally threatened piping plover.

In addition to its mission of wildlife conservation, the refuge provides a variety of excellent wildlife-dependent recreational activities, including surf fishing, wildlife observation and photography, a variety of interpretive programs, and seasonal waterfowl and deer hunting opportunities. A large visitor center, complete with a classroom and auditorium, msupports many of these public uses.

Parker River has achieved the following special designations: Western Hemispheric Shorebird Reserve Network (WHSRN), Important Bird Area (IBA), and Area of Critical Environmental Concern (ACEC).