Elwood is an unincorporated community and census-designated place located within Mullica Township in Atlantic County, in the U.S. state of New Jersey. As of the 2010 United States Census, the CDP's population was 1,437. At previous censuses, the area was listed by the U.S. Census Bureau as the Elwood-Magnolia CDP. The area is served as United …Elwood is an unincorporated community and census-designated place located within Mullica Township in Atlantic County, in the U.S. state of New Jersey. As of the 2010 United States Census, the CDP's population was 1,437. At previous censuses, the area was listed by the U.S. Census Bureau as the Elwood-Magnolia CDP. The area is served as United States Postal Service ZIP Code 08217.