 On November 15, 1824, the westernmost portion of Arkansas Territory was removed and included with the unorganized territory to the north, and a second westernmost portion was removed on May 6, 1828, reducing Arkansas Territory to the extent of the present state of Arkansas.This new western border of Arkansas was originally intended to follow the western border of Missouri due south to the Red River.However, during negotiations with the Choctaw in 1820, Andrew Jackson unknowingly ceded more of Arkansas Territory to them than was realized.