The Platte Purchase was a land acquisition by the United States from the Indians in 1836, adding 8,156 square miles to the state of Missouri so that its northwest boundary now corresponded to the course of the Missouri River.
The Platte River, a tributary of the Missouri, which flows through the area from Iowa, gave its name to this land acquisition.
The region includes present-day Andrew, Atchison, Buchanan, Holt, Nodaway, and Platte counties. The northwestern Kansas City neighborhoods, the cities of Saint Joseph, Mound City, and Maryville, and today’s Kansas City International Airport are located in the Platte Purchase area.
On the so-called Unorganized Territory lived Indians, who had been assured the possession of these territories in perpetuity. Nevertheless, a number of white settlers did not abide by this agreement and demanded the incorporation of the territory settled by them into the state of Missouri.
A treaty was made with the Iowa and United Sauk and Fox tribes at Fort Leavenworth by William Clark. The tribes were paid $7,500; meanwhile, the U.S. government established reservations for the Indians west of the Missouri in Kansas and Nebraska. The Indians undertook to settle there. The Sac and Fox Reservation and the Ioway Reservation still exist there today.
The acquired land was officially annexed to the state of Missouri by President Martin Van Buren in March 1837. The Missouri River now formed the western border of Missouri up to the northern border of the state. Thus Missouri became the largest state in the USA at that time.