1 definition found jamesburg - U.S. Gazetteer (1990) : Jamesburg, NJ (borough, FIPS 34890) Location: 40.34900 N, 74.44017 W Population (1990): 5294 (2064 housing units) Area: 2.2 sq km (land), 0.0 sq km (water) Zip code(s): 08831