The
Platte Purchase was a land acquisition in 1836 by the
United States government from
American Indian tribes. It comprised lands along the east bank of the
Missouri River and added to the northwest corner of the state of
Missouri. This expansion of the slave state of Missouri was in violation of the
Missouri Compromise of 1820, which prohibited the extension of slavery in the former
Louisiana Territory north of the parallel 36°30' north except within the boundaries of the state of Missouri as defined at the adoption of the Missouri Compromise. The area acquired is almost as large as the states of
Delaware and
Rhode Island combined, and extended Missouri north and westward along the river.
St. Joseph, one of the main ports of departure for the westward migration of
American pioneers, was located in the new acquisition.