Hamburg is a Borough in Sussex County, New Jersey, United States. As of the United States 2000 Census, the borough population was 3,105. In 1753, when Sussex County was formed, Hamburg was part of New Town; on February 25, 1762, it became part of the newly established Hardyston Township. On April 8, 1793, when Vernon Township was formed from Hardyston, Hamburg was included within the boundaries of Vernon. In 1852, the boundary line was changed so that Hamburg was again in Hardyston Township. Hamburg was incorporated as a borough on March 19, 1920 from portions of Hardyston Township, based on the results of a referendum held on April 24, 1920.