From 1816 to 1968, the U.S. Army operated a gun and ammunition storage and later production facility known as the Watertown Arsenal. While it was key to many of the nation's war efforts over its several decades in operation, not the least of which being the American Civil War and World War I, its location in Watertown so near the Charles did great environmental harm. The arsenal was declared a Super Fund site, and after its closure by the government it had to be cleaned at significant expense before it could be safely used again for other purposes. Likewise, the many factories and mills along the banks of the Charles supported a buoyant economy in their time but left a legacy of massive pollution.