About 24 square miles in area, the Township of Frelinghuysen offers an immensely varied prospect of mountains, valleys, rivers, marshes, rock ledges, and rolling farmland, as well as a history that is still very much in evidence—from old Indian camps near rivers and lakes to its several historic villages, many historic houses, and other structures, such as mills and lime kilns.
Because the habitats of the Township are so varied and because, until recently, there has not been much development, the Township has a great diversity of wildlife and plant species. Of these habitats, the richest is probably the 565 acres at Mud Pond. At least 23 rare New Jersey plant species have been documented there, making this one of the most species-rich sites in the state. As many as 500 other native species have been found on this site as well.