The Picatinny Arsenal is an American military research and manufacturing facility located on 6,400 acres (26 km²) of land in Jefferson and Rockaway Township in Morris County, New Jersey, United States, encompassing Picatinny Lake and Lake Denmark. The Arsenal is the headquarters of the US Army Combat Capabilities Development Command Armaments Center. It is known for developing the ubiquitous Picatinny rail, as well as being the Army's center of expertise for small arms cartridge ammunition.