Cannonball River and Cannonballs

On Thursday October 18, 1804 Lewis and Clark passed the mouth of the Cannonball River on their way upstream on the Missouri River. Here is a bit of what Clark wrote in his journal for the day:

“Set out early proceeded on at 6 mls passed the mouth of la [Le} Boulet (or Cannon Ball River) about 140 yards on the L.S.(comment mine: L.S means“lar board side” or south or west bank) this river heads in the Court Noi or Black Mountains (a fine Day) above the mouth of the river Great numbers of Stones perfectly round with fine Grit are in the Bluff and on the Shore, the river takes its name from those Stones which resemble Cannon Balls. The water of this river is confined within 40 yards.”

The Cannonball River was, of course, named after the interesting cannonball-like concretions that may be found along the river. The river heads just north of Amidon in Slope County. From there it flows southeastward through New England, Regent, and Mott, to near where highway 31 intersects the border of Grant and Sioux County. From there it flows northeastward forming the Grant-Sioux County line before flowing into the Missouri River near Cannonball. Although the flows of this 135 mile river may be negligible during dry periods, it can flow to perhaps 95,000 cubic feet per second during wet periods.

Cannonball concretions are one of the more interesting geological features found in the state. These sandstone concretions are formed when water flows through sandstone. A bit of shell or plant material may form a nucleus upon which cementation of calcium carbonates or other mineral compounds begin to enlarge the concretion. Although generally less than two or three feet in diameter, some cannonball concretions have been reported to be up to 10 feet in diameter. Because they are often more resistant to erosion than the surrounding material, erosion often removes the surrounding material thus exposing the concretions.

No doubt many of you have noticed concretions in other locations in the state as well. Spherical, cylindrical, and other shaped concretions may be found in and around the badlands, and are readily observed in Theodore Roosevelt National Park. But the cannonball concretions are perhaps most commonly observed as lawn ornaments and conversation pieces in lawns and homes in the Bismarck-Mandan areas and other areas in the western part of the state.

Chuck Lura

Natural North Dakota is supported by NDSU Central Grasslands Research Extension Center and Minot State University-Bottineau, and by the members of Prairie Public. Thanks to Sunny 101.9 in Bottineau for their recording services.