Maplewood, New Jersey. Maplewood is a suburban township in Essex County, New Jersey, United States. As of the 2010 United States Census, the township's population was 23,867, reflecting a decline of 1 person (0.0%) from the 23,868 counted in the 2000 Census, which had in turn increased by 2,216 (+10.2%) from the 21,652 counted in the 1990 Census. 1 History.