They are one of those four North Dakota Indian groups--Mandan, Hidatsa, Cheyenne, and Arikara--who because of their farming activities are called the agricultural tribes. While the Mandan were building on the Missouri, the Hidatsa were probably living somewhat farther north and east. They have a tradition that they originally came from a large lake to the east, possibly Devils Lake. Later, probably forced on by some other tribe, they moved their families over the prairies to the Missouri in the region of the Heart River, and eventually allied themselves with the Mandan. Their history thereafter follows very closely that of the latter tribe. While the Mandan and Hidatsa were dwelling on the Missouri, the Cheyenne were migrating westward from the headwaters of the Mississippi, by way of Lac Que Parle in present Minnesota, Lake Traverse, and the big bend of the Sheyenne River, to the Missouri, seeking a place where they could till the soil and rear their children in peace, free from the harrying of the Sioux. At the same time the Arikara, doubtless likewise trying to take their families away from the ravaging Dakota, were ascending the Missouri. The name of this tribe arose from their custom of wearing in their hair two pieces of bone which stood up on each side of the head like horns. They came from the southwest and their language differs only in dialect from the Pawnee. In 1770 French traders encountered them dwelling along the river bank somewhat below the mouth of the Cheyenne River in what is now South Dakota. The migrations of the Hidatsa, Cheyenne, and Arikara, as those of the Mandan, are traceable by the old village sites, of which there are about 75 known locations on the prairies of the State. Arikara sites predominate lower down the Missouri in South Dakota; the older Mandan--perhaps constructed as early as 1575-1650--in the Heart River region; and the Hidatsa, farther north near the Knife River. There are apparently two types, a newer and an older. The newer, perhaps less carefully laid out than the older, is found at and above the mouth of the Heart River. The older type appears to have had better fortifications than the newer, and the lodges do not seem to have been so crowded. Because of its greater age it is more heavily sodded, and thus manufactured articles left by the village dwellers, such as stone and bone tools and ornaments, are less easily recovered. It seems to center below the Heart River, with the Huff site, just below the village of Huff, as perhaps the best example (_see Tour 8_). Sometime--perhaps a hundred years--after the Mandan first built about the mouth of the Heart River, the three nomadic North Dakota tribes--the Sioux, Assiniboin, and Chippewa--were ranging the forests near the headwaters of the Mississippi. The Chippewa, however, were not strictly nomadic, as they had more or less permanent camping places, where they built their distinctive bark shelters.