A remote prairie river flowing through the Standing Rock Reservation — the Cannonball is named for the perfectly round sandstone concretions found along its banks, which early explorers mistook for cannonballs. One of the most isolated paddling experiences in North Dakota, through vast grasslands with virtually no development. The 140-mile river cuts from narrow headwaters in Slope County east across the prairie to the Missouri confluence through Standing Rock.
River conditions are community-verified. CFS ranges, difficulty ratings, and trip sections may not reflect every flow level or seasonal change. Always check current conditions, scout unfamiliar rapids, and paddle within your skill level. If you spot an error, use the Improve This River button at the top of the page — your local knowledge is what makes this atlas accurate.