11791 -- U.S. ZIP code Municipality (1990): SYOSSET, New York All ZIPs for this municipality (1990): 11791 Population (2000): 24445 Housing Units (2000): 8239 Land area (2000): 11.205925 sq. miles (29.023211 sq. km) Water area (2000): 0.162350 sq. miles (0.420484 sq. km) Total area (2000): 11.368275 sq. miles (29.443695 sq. km) Located within: New York (NY) Location: 40.815215 N, 73.500577 W