Northfield is a city in Atlantic County, New Jersey, United States. As of the 2010 United States Census, the city's population was 8,624, reflecting an increase of 899 from the 7,725 counted in the 2000 Census, which had in turn increased by 420 from the 7,305 counted in the 1990 Census.Northfield was incorporated as a city by an act of the New Jersey Legislature on March 21, 1905, from portions of Egg Harbor Township. A portion of Egg Harbor Township was transferred to Northfield in 1931, and then reverted to Egg Harbor Township in 1933.The city calls itself the "Gateway to the Shore", just over the bridge from the beaches, and is located about 7 miles west of Atlantic City, bordering the municipalities of Pleasantville, Egg Harbor Township and Linwood.