The Millstone River is a scenic 38.6-mile waterway in central New Jersey, originating near Millstone Borough and flowing northward to its confluence with the Raritan River near Manville. As a major tributary of the Raritan, it forms an integral part of the Raritan River watershed. Paddling opportunities on the Millstone River range from peaceful flatwater sections to occasional Class I rapids, making it suitable for beginners to intermediate paddlers. The river is closely paralleled by the historic Delaware and Raritan (D&R) Canal for much of its length, offering paddlers the unique option to explore both waterways.

Popular sections include the stretch from Blackwells Mills to Griggstown (about 5.5 miles) and the Princeton area, where paddlers can combine trips on the river with Lake Carnegie and the D&R Canal. The river is best paddled in spring, summer, and fall, with water levels typically most favorable from March to June. Summer paddling is pleasant but may require occasional portaging in low water conditions.

The Millstone River valley supports a diverse ecosystem, with paddlers likely to encounter great blue herons, turtles, and a variety of fish species. The surrounding landscape features a mix of wetlands, forests, and historic farmlands. Key points of interest include the preserved canal villages of Griggstown and Blackwells Mills, each with their own historic bridge tender's houses. The river passes through Princeton, offering views of the prestigious university town. The Millstone River Park near Princeton provides an excellent access point for exploring the river's marsh areas.

Primary access points include Weston's Mill Pond in East Brunswick, Blackwells Mills, Griggstown, and various locations in Princeton. These access points are typically well-maintained with parking facilities. Many are part of the D&R Canal State Park, which offers additional amenities and historical interpretation.

The Millstone River holds significant historical importance, having powered numerous mills in the 18th and 19th centuries that gave the region its name. The adjacent D&R Canal, once a crucial transportation route, now serves as a recreational gem alongside the river.

Paddlers should be aware of occasional low-head dams and should always check water levels before embarking. The river is generally calm, but can become swift after heavy rains. Multi-day trips are possible by combining river paddling with sections of the D&R Canal, with numerous bed and breakfasts and campgrounds available in the historic towns along the route.

For those seeking a quintessential central New Jersey paddling experience, the Millstone River offers a perfect blend of natural beauty, historical significance, and accessible adventure.