After the United States took possession of the Louisiana Territory in March 1804, American control expanded into Osage country and U.S. attitudes toward the Osage shifted rapidly by around 1808, especially as raids on increasing numbers of American settlers drew government wrath. In the summer of 1806, Zebulon Pike traveled up the Missouri and Osage rivers, returned several captive Osage, spent several days with them, and left an account that provided information on the river and sites relating to the Osage. In May 1808, the U.S. War Department decided to establish Fort Osage, built along the Missouri River just east of present-day Kansas City and named after General William Clark, to serve as a fort and trading post, help obtain Osage lands, confine the Osage to the western part of the state, and make raids on eastern settlements more difficult. On September 12, 1808, chiefs and warriors of the Big Osage and Little Osage met in a council arranged by Clark, and two days later agreed to a treaty creating a dividing line between American land and Osage hunting grounds, but the treaty collapsed when the Arkansas River Osage rejected it and others said they did not understand it; it was signed again on November 10, 1808, and ratified by the Arkansas River Osage on August 31, 1809. As the Osage became dependent on European goods, traded furs and skins to pay for them, lost hunting land, faced scarcer game, and fell into debt they could not repay, the government forced them to surrender more land, and in 1825 they ceded their remaining land in Missouri. In 1819 the Osage began requesting missionaries, and a mission party from New York established Harmony Mission in August 1821 on the Marais des Cygnes River near the trading post directed by George Sibley; after many Osage moved to Kansas and Oklahoma, the mission closed in 1827. After repeated removals, the Osage ended up on a small reservation in Oklahoma, and by the late 19th century their hunting, warring, and nomadic way of life had passed as they adapted peacefully to a new life forced upon them.