In its more than two centuries of existence, the Washington Navy Yard has experienced both physical growth and significant changes in mission. Initially established as a storage and shipbuilding facility, in the middle of the Nineteenth Century it was changed to a heavy industrial plant, primarily concerned with the development, construction and testing of naval guns. The facility grew significantly as the Navy expanded during the early 1900s and during the two World Wars, when it produced much of the ordnance material that armed the fleet. Its name was formally changed to Naval Gun Factory soon after the end of World War II, and again to Naval Weapons Plant in 1959 as guided missiles displaced guns as the Navy's principal shipboard armament. However, within a few years, as part of a general Defense Department shift away from Government-owned production facilites, the Plant's industrial work ceased, much of its land was diverted to non-Navy uses and its name reverted to Washington Navy Yard. During the subsequent four decades, it emerged as a major administrative center, with a considerable historical presence, and has recently seen many of its old industrial buildings modified for new purposes or replaced by more modern structures.