21128 -- U.S. ZIP code Municipality (1990): PERRY HALL, Maryland All ZIPs for this municipality (1990): 21128 Population (2000): 6703 Housing Units (2000): 2755 Land area (2000): 6.588070 sq. miles (17.063022 sq. km) Water area (2000): 0.000406 sq. miles (0.001051 sq. km) Total area (2000): 6.588476 sq. miles (17.064073 sq. km) Located within: Maryland (MD) Location: 39.400296 N, 76.446398 W