They pitched their camp, which they called Fort Mandan, on the eastern shore of the Missouri, near the present city of Bismarck. They built some wooden huts, which formed two sides of a triangle, and a row of pickets on the third side, to provide them with a stockade in case of attack. They found a trader of the Hudson's Bay Company near by, and during the winter a dozen other traders visited them. Although they appeared to be friendly, Captain Lewis was convinced that the traders had no desire to see this United States expedition push into the country, and would in fact do all they could to prevent its advance. The Indians in the neighborhood belonged to the tribes of the Mandans, Rickarees, and Minnetarees. The first two of these tribes went to war early in the winter, but peace was made through the efforts of Captain Lewis. After that all the Indians visited the encampment, bringing stores of corn and presents of different sorts, in exchange for which they obtained beads, rings, and cloth from the white men. Here Captain Lewis learned a curious legend of the Mandan tribe. They believed that all their nation originally lived in one large village underground near a subterranean lake, and that a grape-vine stretched its roots down to their home and gave them a view of daylight. Some of the more adventurous of the tribe climbed up the vine, and were delighted with the sight of the earth, which they found covered with buffaloes and rich with all kinds of fruits. They gathered some grapes and returned with them to their countrymen, and told them of the charms of the land they had seen. The others were very much pleased with the story and with the grapes, and men, women and children started to climb up the vine. But when only half of them had reached the top a heavy woman broke the vine by her weight, and so closed the road to the rest of the nation. Each member of this tribe was accustomed to select a particular object for his devotion, and call it his "medicine." To this they would offer sacrifices of every kind. One of the Indians said to Captain Lewis, "I was lately the owner of seventeen horses; but I have offered them all up to my 'medicine,' and am now poor." He had actually loosed all his seventeen horses on the plains, thinking that in that way he was doing honor to his god.