The ancient habitat of the Arapaho, according to tradition, was once far northeast of the country which they later occupied. It may have been among the forests of the region about the headwaters of the Mississippi, the present State of Minnesota, where their villages would have stood on the shores of lakes and streams. But later, like the related Cheyenne, with whom they have been closely allied during recent generations and probably for a long period, they reached the prairies, through what causes may never be known, and there, with different environments, their manners and ways of life changed. While a people of the timbered country, they undoubtedly reared and occupied the forms of habitations so characteristic of the forests, as exemplified by the wigwams of the Ojibway and other tribes in recent times, but after reaching the prairie country, where buffalo were obtained in such vast numbers, their villages or camps assumed the appearance of those of the Siouan tribes, conical skin lodges taking the place of the mat or bark covered structures. The Atsina, a detached division of the Arapaho, closely associated with the Blackfeet, were often mentioned by the early writers as the Gros Ventres of the Prairie, and in certain English narratives as the Fall or Rapid Indians. In other journals they were mentioned under the name Minnetarees of Fort de Prairie. Thus they were called by the early American explorers. On May 29, 1805, just two weeks before arriving at the Great Falls of the Missouri, the Lewis and Clark party reached Judith River, and a short distance above its junction with the Missouri "We saw the fires of one hundred and twenty-six lodges, which appeared to have been deserted about twelve or fifteen days, and on the other side of the Missouri a large encampment, apparently made by the same nation. On examining some moccasins which we found there, our Indian woman said that they did not belong to her own nation the Snake Indians, but she thought that they indicated a tribe on this side of the Rocky mountains, and to the north of the Missouri; indeed it is probable that these are the Minnetarees of fort de Prairie." (Lewis and Clark, (1), I, p. 234.) The following year, when the expedition was returning from the west, the tribe was again mentioned. On July 15, 1806, the expedition passed Shields River, and two days later reached Brattons River (now Bridger Creek), a tributary of the Yellowstone in the present Sweetgrass County, Montana. Here, "In one of the low bottoms of the river was an Indian fort, which seems to have been built during the last summer. It was built in the form of a circle, about fifty feet in diameter, five feet high, and formed of logs, lapping over each other, and covered on the outside with bark set up on end, the entrance also was guarded by a work on each side of it, facing the river. These intrenchments, the squaw informs us, are frequently made by the Minnetarees and other Indians at war with the