Railway gun
Baldwin Locomotive Works made five 14"/50 caliber railway guns on trains for the United States Navy during April and May 1918.  Each train carried a Mk 4 14"/50 caliber gun. These were a  naval rifle used on New Mexico and Tennessee class battleships, mounted on a rail carriage with four 6-wheel bogies. One of these guns is on display outside the museum at the Washington Navy Yard.