Treaty of Fort Clark
The Treaty of Fort Clark (also known as the Treaty with the Osage or the Osage Treaty) was signed at Fort Osage (then called Fort Clark) on November 10, 1808, (ratified on April 28, 1810) in which the Osage Nation ceded all the land east of the fort in Missouri and Arkansas north of the Arkansas River to the United States. The Fort Clark treaty and the Treaty of St. Louis in which the Sac (tribe) and Fox (tribe) ceded northeastern Missouri along with northern Illinois and southern Wisconsin were the first two major treaties in the newly acquired Louisiana Purchase. The affected tribes, upset with the terms, were to side with the British in the War of 1812. Following the settlement of that war, John C. Sullivan for the United States was to survey the ceded land in 1816 (adjusting it  westward to the mouth of the Kansas River to create the Indian Boundary Line west of which and south of which virtually all tribes were to be removed in the Indian Removal Act in 1830. Background
When Lewis and Clark began their explorations of the Missouri River in 1804, Pierre Chouteau of the Chouteau fur trading family in St. Louis, Missouri took Osage chiefs to meet Thomas Jefferson who promised to open a government sanctioned trading post (then called the factory which the Osage could sell their goods at a government set price (ostensibly to keep them from being exploited by individual traders). The trading post would also have a blacksmith to provide utensils for the Native Americans. In early 1808, Meriwether Lewis led a group to the site of Fort Osage near Sibley, Missouri where they built the fort on a bluff above the Missouri River. Pierre Chouteau went about 150 miles south to Neosho, Missouri where the Osage had their principal village on the Osage River and brought the chiefs to Fort Osage. There they were presented with the terms of the treaty. Terms

Ceded land
The treaty specifically cedes the following land:

Payment
According to the Article V, the Osage were to receive an annual payment:

Ceded lands
In Article VI the lands ceded:

Assignment to other tribes
Article VIII provided that the Osage land could be assigned to other tribes:

Aftermath
There were protests immediately from the tribe as there were claims that not all the proper representatives signed the document. The Osage for the most part did not move to Fort Osage staying instead at their home in Neosho. Some tribesmen were to side with the British in the War of 1812. After the war, the Osage were summoned to Portage Des Sioux, Missouri where they affirmed the treaty in the Treaties of Portage des Sioux in 1815. See also
 Osage Treaty (disambiguation), several treaties
 List of treaties
 Lovely's Purchase

Sources

External links
Kappler Project – Text of Treaty
The Osage: A Historical Sketch

Fort Clark
Fort Clark
1808 in the United States
Pre-statehood history of Missouri
Pre-statehood history of Arkansas
1810 treaties
1808 treaties