Nassau County, FL (county, FIPS 89) Location: 30.61069 N, 81.76766 W Population (1990): 43941 (18726 housing units) Area: 1687.7 sq km (land), 192.4 sq km (water) Nassau County, NY (county, FIPS 59) Location: 40.73279 N, 73.58840 W Population (1990): 1287348 (446292 housing units) Area: 742.7 sq km (land), 431.4 sq km (water)