Elmer is a Borough in Salem County, New Jersey, United States. As of the United States 2000 Census, the borough population was 1,384. Elmer was incorporated as a borough by an Act of the New Jersey Legislature on January 28, 1893, from portions of Pittsgrove Township and Upper Pittsgrove Township, based on the results of a referendum held four days earlier. The borough was formed on the dividing line of Pittsgrove and Upper Pittsgrove Townships and was named for Lucius Elmer a former judge who helped obtain a post office for the community during his service as Congressman.