Bellmawr is a borough in Camden County, New Jersey, United States. As of the 2010 United States Census, the borough's population was 11,583, reflecting an increase of 321 from the 11,262 counted in the 2000 Census, which had in turn declined by 1,341 from the 12,603 counted in the 1990 Census.Bellmawr was incorporated as a borough on March 23, 1926, from portions of the now-defunct Centre Township, based on the results of a referendum held on April 21, 1926. The boroughs of Mount Ephraim, Runnemede and Lawnside were also created in the same two-day period. The borough was named for Ernest C. Bell.Bellmawr is home to the main post office for the area, one of the largest in the state of New Jersey, handling an average of 4.5 million pieces of mail daily. In late October 2001, the office was closed due to possible anthrax contamination in the wake of the 2001 anthrax attacks. The office was re-opened several days later, in early November, after testing negative for anthrax.