Cedar Swamp Archeological District is a historic district in eastern Westborough, Massachusetts, and extending into the northwest corner of Hopkinton. Cedar Swamp is an area of more than 1,600 acres (650 ha) of wetlands that include the headwaters area of the Sudbury River. Archeological surveys of the environmentally sensitive and critical area have identified Native American sites of interest. It is believed that Native Americans prized wood from the cedar trees that grew in the area.