21561 -- U.S. ZIP code Municipality (1990): SWANTON, Maryland All ZIPs for this municipality (1990): 21561 Population (2000): 2608 Housing Units (2000): 2311 Land area (2000): 104.271024 sq. miles (270.060701 sq. km) Water area (2000): 0.529325 sq. miles (1.370946 sq. km) Total area (2000): 104.800349 sq. miles (271.431647 sq. km) Located within: Maryland (MD) Location: 39.484412 N, 79.208561 W