High Quality Content by WIKIPEDIA articles! Princeton Township is a township in Mercer County, New Jersey, United States. As of the United States 2000 Census, the township population was 16,027.Princeton was incorporated as a township by an Act of the New Jersey Legislature on April 9, 1838, from portions of West Windsor Township in Middlesex County and Montgomery Township in Somerset County. The Borough of Princeton ? created on February 11, 1813 within the area that later became Princeton Township ? became a fully independent municipality circa 1894. Portions of territory were ceded to the Borough of Princeton on January 4, 1928 and August 21, 1951.