Spotswood is situated at the confluence of the Manalapan and Matchaponix, which form the South River. These waterways provided natural power for a series of industries, beginning with a saw mill established by the 1720s by noted regional Lenape Indian leader, Weequehela. By the 1730s, the Johnston brothers took over the site, giving their name to the settlement prior to "Spotswood".
During the American Revolution, local militia raided the mills, at the time controlled by Loyalist owners, and hauled off large quantities of supplies including iron and over 5,000 pounds of meat, The mills were later put under guard by the militia to prevent any similar British attacks.
After the Revolution, the mill seat was used as a saw mill, paper and grist mill, and by the 1850s, snuff manufacturing.
Operations ceased by the 1920s
Grant funding has been provided by the Middlesex County Cultural and Heritage Commission, Middlesex County Board of Chosen Freeholders through a grant provided by New Jersey Historical Commission, a Division of Dept. of State