Washington Navy Yard Created in 1799, the Washington Navy Yard in Washington D.C. quickly became the nation's largest base of shipyard operations for the U.S. Navy. During the War of 1812, the base commander ordered the facility burned as British soldiers entered the city, and it was rebuilt after hostilities had ceased. Soon the shipyard was again operating at full capacity and both during and after the Civil War in the 1860s, the yard became more of an ordnance facility, focusing on engineering developments and technological advances for newer vessels. By the Second World War, the facility was the primary development and manufacturing plant for a variety of naval armaments, especially the large guns and antiaircraft production that was vital to the modern destroyers and battleships of the period. It no longer served as a major shipbuilding yard, primarily because the shallow waters of the Potomac River did not allow for the largest vessels to be constructed efficiently. At its height as a research, design and ordnance facility, the Washington Navy Yard employed over 25,000 workers. At the conclusion of World War II, the base was renamed the U.S. Naval Gun Factory. However, as the modern shipbuilding industry changed and the era of nuclear powered ships and submarines began, an assortment of manufacturing centers across the country began to take its toll on the production of weapons at the facility. Finally, in 1961, manufacturing was phased out and the area was redesignated the Washington Navy Yard, occupied now by offices, museums, and historical sites. The yard is home to the Chief of Naval Operations and the headquarters of the Naval Historic Center. Over the years, an enormous amount of hazardous materials and chemicals were used at the facility, among them toxic paints, lead, and asbestos. The latter was often part of insulations and fire retardants, both in the buildings on the site and in the vessels themselves. Thousands of these workers were exposed to asbestos fibers, which are a known cause of several types of cancer, including mesothelioma and asbestosis. Asbestos fibers pass through the air and can also remain embedded in skin, clothing, and shoes. Workers also often introduced asbestos into their homes, thus exposing their family members. Symptoms of diseases resulting from exposure to asbestos often do not show for many years, and it is unclear how many past workers at the Washington Navy Yard are subject to malignant or benign forms of cancer because of the conditions under which they were employed.