Sparta Township is a township in Sussex County, New Jersey, United States. As of the 2010 United States Census, the township's population was 19,722, reflecting an increase of 1,642 (+9.1%) from the 18,080 counted in the 2000 Census, which had in turn increased by 2,923 (+19.3%) from the 15,157 counted in the 1990 Census. Sparta was organized as a township by an act of the New Jersey Legislature on April 14, 1845, from portions of Byram Township, Frankford Township, Hardyston Township and (the now-defunct) Newton Township. The township was named after the existing community of Sparta, which had been settled and named years before, the name likely coming from Sparta, Greece. Ogdensburg borough was incorporated on February 26, 1914, when it separated from Sparta Township.