The main armory stretched over two city blocks in what was known as the Hill Shops (where the National Historic Site now is accompanied by the Springfield Technical Community College which occupies most of the 22 original buildings). About one mile (1.6 km) south, on the Mill River, the United States Army built the Water Shops where the heavy metal forging and machining was done as well as gun stock shaping. It was located there to take advantage of the water power supplied by the Mill River. The facilities were developed between 1857 and 1941, including a number of buildings and a dam and canal to raise the level of Watershops Pond when the demand for water power was increased.
The Water Shops complex is now a privately owned industrial site. The main building was severely damaged on Friday June 17, 1988, when a fire destroyed part of the top floors. The building was built in two different sections: the first was built in 1858, and the second section, which paralleled Allen Street and was built in 1901, is where the fire happened.