Stillwater River

The Stillwater River is part of the Nashua River watershed. This river is part of the Massachusetts Water Resources Authority system that supplies drinking water to the greater Boston area. The Stillwater River rises in Princeton, Massachusetts, the watershed generally known as the Upper Worcester Plateau, or the Monadnock Upland. 

This watershed tops at Wachusett Mountain, the highest feature in the area. Water flowing east from this high ground feeds the Nashua River Watershed, and water flowing west feeds the Ware River or the Millers River, both heading to the Connecticut River.The Stillwater flows 8.1 miles (13.0 km) through Princeton and Sterling before joining the Quinapoxet River at the Wachusett Reservoir in West Boylston to form the south branch of the Nashua River.