At 15 m. is the junction with a graveled road.
Right here is ST. ANTHONY, 0.5 m. (1,790 alt., 116 pop.), a small community settled in 1887 by Roman Catholic German-Hungarians from Ohio. In 1906 a parochial school was opened, and despite the small size of the community this institution is still in operation, with an enrollment of more than 120.
The highway enters range country with few fences or farms. At 26 m. is a junction with ND 21 (see Side Tour 4B), which unites with ND 6 to 33 m. Here, as the highway begins to descend into the valley of the Cannonball River, there is a far-reaching view of country severe and imposing. Steep grass-covered hills and mesas give way to sharp, abrupt, gray clay cones and buttes that rise in confusion from the plain. The work of erosion in the creation of these formations is visible in many sidehills, where the top layers of earth have worn away to expose the bedrock strata beneath.
At 32 m. is the junction with a graveled roadbed.
Right here is BREIEN, 1 m. (1,694 alt., 53 pop.). Between the highway and the town is a natural park with camping facilities.
The CANNONBALL RIVER is crossed at 32.5 m. The river, its thin fringe of trees contrasting with the gray-brown of the valley, is so named because of the odd spheroidal formations found in its waters and in the steep banks of its valley. These concretions, believed to have been formed by the action of moisture within the Fox Hills sandstone, have been carried away in such large numbers by collectors that today only the small "cannonballs" are found along the stream. The Cannonball was the northern boundary of the Standing Rock Reservation before the area was opened to white settlement in 1910, and now is the northern limit of jurisdiction of the agency.
Left at 33 m. on ND 21, an unimproved dry-weather roadbed; the route passes through rugged hills S. of the Cannonball, reaching SOLEN, 40 m. (1,671 alt., 103 pop.), on the riverbank.
The route continues through country occasionally dotted with the small frame buildings of white farmers and the log huts of Indian families.
At 49 m. is the junction with ND 24, a graveled highway; R. on this route.
Left from the junction with ND 24 on ND 21 to the junction with an unimproved road, 1 m.; straight ahead (N) 0.3 m. to the steep western slope of the HOLY HILL OF THE MANDANS (R). Almost every tribe of American Indians has a tradition of a great flood which covered all the earth. The Mandan legend tells that an ark came to rest on this hill near the Cannonball River, and after the waters subsided the First Man and First Woman stepped out on the hill. Mandan, Arikara, and Sioux all revere the place, and the older natives are reticent about approaching the hilltop.