This park contains two units, Birch Creek and Nails Creek, connected by a 13-mile trailway system. Both units of Lake Somerville State Park offer a multitude of recreational opportunities such as camping, picnicking, boating, fishing, hiking and biking, volleyball, horseshoes, basketball, backpacking and equestrian use (visitors must bring their own horses). More than 20 miles of trail are open to hikers, mountain bikers and equestrians, affording visitors the opportunity to exercise and enjoy the beauty of the park. Water lovers can enjoy boating, fishing, swimming and skiing on Lake Somerville.

Flag Pond, located approximately 4 miles from Nails Creek State Park and 9 miles from Birch Creek State Park along the Somerville Trailway, provides waterfowl hunting and non-consumptive wildlife viewing opportunities in conjunction with a system of interpretive trails, nature study, outdoor classrooms, and wildlife photography. The Flag Pond Nature Theater provides an excellent wildlife-viewing platform.