REMARKS: Erosional remnants of a large and unusual outcrop of enstatite rock forms a "castle-like" appearance; from the top of the "castle-towers" on can view the countryside. C. E. Hall wrote in 1885 that Castle Rock "was known as a romantic spot" (p. 38 in reference below). Today, a housing development surrounds the feature.
REFERENCES: Hall, C. E. [1885], Field notes in Delaware County, Pennsylvania Geological Survey, 2nd ser., Report C5, 128 p.
REMARKS: The largest saltwater marsh in Pennsylvania; also a freshwater marsh and lake in the east and northeast areas. The U. S. Fish and Wildlife Service, Department of the Interior, owns and operates the freshwater section. The Tinicum Environmental Center is located south of 84th Street along Darby Creek at the head of the marsh; a registered National Natural Landmark.