the Great Salt Plains by 1760 and because of a favorable combination of geographical factors, the Osages became the dominant force in mid—America. "In a one hundred twenty-five year period, 1678-1803, the Osages performed a feat no other American Indians duplicated," writes Burns. "They stopped the west-ward expansion of the Euro-American peoples and simultaneously tripled the size of their own domain." Sibley Expedition George Champlin Sibley was appointed head trader at the Indian Factory at Fort Osage, Missouri, when it opened in 1808. While at Fort Osage, Sibley quickly engaged in creating relationships with the neighboring Osage tribes. In May 1811 Sibley's expedition left Fort Osage to examine the hunting grounds of the Osage. In 1811 his expedition was said to be the first white men said to visit the plains. Sibley's expedition, leaving from Fort Osage, Missouri was guided by an Osage Indian named Sans Orielle. Sibley named the area the Grand Saline. Sibley cut short his expedition when informed by reports that bands of Comanche were nearby. Sibley returned to Fort Osage on July 11, 1811 and reported that the salt deposits would eventually prove commercially profitable. Native American Usage The Great Salt Plains have been the scene of many Indian Councils, both of war and peace. Because animals flocked to the area for the salt, the Great Salt Plains made for excellent hunting and it became obvious that any tribe that controlled the Salt Plains would have to contend with intrusions by other tribes. Therefor the Treaty of New Echota signed in 1835, provided the Cherokee Nation with ownership of the Cherokee Outlet but declared that the saline areas were to be accessible to use by other tribes. In drafting the treaty the United States Government withheld the Salt Plains area with the provision that, "The right is reserved to the United States to allow other tribes of red men to get salt on the Great Salt Plains in common with the Cherokee Tribe." Chemical weapons discovery In 2007, a Boy Scout digging for crystals uncovered a collection of 7.5-inch vials containing chemical agents such as mustard gas, lewisite, chloropicrin, and phosgene. The vials were part of World War II-era military chemical agent identification sets. The burial of vials was standard procedure for removing them from service at that time. No record of a disposal site was reported at the salt plains. Crystal digging was suspended from