The Ontonagon River system drains a large portion of Michigan's western Upper Peninsula, flowing northward into Lake Superior. It consists of four main branches - the West, South, Middle, and East - which converge to form the main stem Ontonagon River. The West Branch originates at Lake Gogebic and flows approximately 35 miles northeast before joining the South Branch. The Middle and East Branches merge upstream of their confluence with the main stem near the town of Ontonagon.

Paddlers can find a range of experiences across the river system, from calm flatwater to challenging whitewater. The Middle Branch is particularly popular, with several scenic day-trip options. A 6.4-mile stretch from Burned Dam Campground to Interior Bridge offers mostly Class I rapids with occasional Class II sections, suitable for intermediate paddlers. Downstream, the 5-mile segment from Interior Bridge to Bond Falls Flowage continues the scenic journey with similar difficulty. More advanced paddlers can test their skills on the West Branch, where a 5.3-mile section from Victoria Falls Dam to Victoria Dam Road features Class III-IV rapids. The East Branch also provides exciting whitewater, with a 7.5-mile run from East Branch Road to Highway 45 rated Class II-III.

Spring typically offers the highest water levels, though summer paddling is possible on many sections. The river system supports diverse wildlife, including brown trout, steelhead, and salmon. Bald eagles and other raptors are frequently spotted along the forested banks.

Key landmarks include Bond Falls, a spectacular 50-foot cascade on the Middle Branch, and the historic Victoria Dam on the West Branch. Watersmeet serves as a primary access point for Middle Branch trips, while the town of Ontonagon provides access to the lower main stem.

The Ontonagon River played a significant role in the region's copper mining history, with the famous Ontonagon Boulder - a 3,708-pound mass of native copper - discovered along its banks in 1667. Today, much of the river corridor is protected within Ottawa National Forest, preserving its natural beauty and recreational value.

Paddlers should be aware of potential hazards like strainers and cold water, especially during high flows. Some sections require portaging around dams. Multi-day trips are possible on the main stem and larger branches, though camping options may be limited in some areas.