At the mouth of the Bad River, in today's Fischers Lilly Park, Lewis and Clark had their long-awaited first meeting with the Lakota people known to them as the Teton Sioux. As the Lakota controlled this stretch of the waterway, Jefferson and his commanders knew that establishing a positive relationship was critical to the success of U.S. interests in North American trade. The expedition spent five days feasting and in council with Chiefs Black Buffalo, Buffalo Medicine, the Partisan, and the Lakotas. Tensions and mutual mistrust were high, leading on two occasions to the shouldering of arms. Lewis and Clark left the area on September 28, 1804, without achieving their goal of a Lakota pledge for peaceful trade with the Americans.