For mounting bracket used on some firearms, see Picatinny rail. The Picatinny Arsenal (/ˈpɪkətɪni/ or /ˌpɪkəˈtɪni/) is an American military research and manufacturing facility located on 6,400 acres (26 km2) of land in Jefferson Township and Rockaway Township in Morris County, New Jersey, United States, encompassing Picatinny Lake and Lake Denmark.