Watertown Arsenal The Watertown Arsenal was a major American arsenal located on the northern shore of the Charles River in Watertown , Massachusetts . Its site is now registered on the ASCE ' s List of Historic Civil Engineering Landmarks and on the U . S . ' s National Register of Historic Places , and it is home to the Arsenal Mall , a park , restaurants , and many offices . History . The arsenal was established in 1816 , on of land , by the United States Army for the receipt , storage , and issuance of ordnance . In this role , it replaced the earlier Charlestown arsenal . The arsenal ' s earliest plan incorporated 12 buildings aligned along a north - south axis overlooking the river . Alexander Parris , later designer of Quincy Market , was architect . Buildings included a military store and arsenal , as well as shops and housing for officers and men . All were made of brick with slate roofs in the Federal style , and a high wall enclosed the compound . By 1819 all buildings were completed and occupied . The arsenal ' s site , duties , and buildings grew gradually until the American Civil War , enlarging beyond the original quadrangle . During the war it greatly expanded to produce field and coastal gun carriages , and the war ' s impetus led to the quick construction of a large machine shop and smith shop built as contemporary factories , as well as a number of smaller buildings . During the Civil War , a new commander ' s quarters was commissioned by then - Capt . Thomas J . Rodman , inventor of the Rodman gun . The lavish , , quarters would ultimately become one of the largest commander ' s quarters on any U . S . military installation . This mansion is now on the National Register of Historic Places . The expense ( $ 63 , 478 . 65 ) was considered wasteful and excessive and drew a stern rebuke from Congress , who then promoted Rodman to Brigadier General and sent him to command Rock Island Arsenal on the frontier in Illinois , where he built an even larger commander ' s quarters . Activities and new construction at the Watertown Arsenal continued to gradually expand until the early 1890s . Activities changed decisively in 1892 when Congress authorized modernization to gun carriage manufacturing . At this point the arsenal became a manufacturing complex rather than storage depot . A number of major buildings were constructed , which over time began to reflect typical industrial facilities rather than the earlier arsenal styles . In 1897 an additional were purchased , and a hospital built . Scientific management was implemented at the arsenal between 1908 and 1915 . It was considered by the War Department as successful in saving money over the alternatives ; but it was so hated by the work force that the Congress eventually overturned its use . During World War I the arsenal nearly tripled in size . Building # 311 was then reported to be one of the largest steel - frame structures in the United States , sized to accommodate both very large gun carriages and the equipment used to construct them . Railroad tracks ran throughout the arsenal complex . World War II brought an additional with existing industrial buildings , as the arsenal produced steel artillery pieces . In 1959 – 1960 , the Horace Hardy Lester Reactor was constructed on site , for material research programs , and operated there until 1970 . In 1968 the Army ceased operations at the arsenal ; were sold to the Watertown Redevelopment Authority , while the remaining were converted to the United States Army Materials and Mechanics Research Center ( AMMRC ) , renamed the United States Army Materials Technology Laboratory ( MTL ) in 1985 . In 1995 all Army activity ceased and the remainder of the site was converted to civilian use . The Armory site was formerly included on US EPA ' s National Priorities List of highly contaminated sites , more widely known as Superfund . The site was removed from the NPL in 2006 . The largest buildings at the site are now home to the aptly named Arsenal Mall .