American Powder Mills (1883-1929) was a Massachusetts gunpowder manufacturing complex on the Assabet River. It expanded to include forty buildings along both sides of the river in the towns of Acton, Concord, Maynard, and Sudbury. Press mills, kernelling mills, glazing mills, and storehouses were dispersed over four-hundred acres to minimize damage during explosions. A narrow gauge railway transferred raw materials and products between the buildings.