(A treaty is a contract between two groups.  Usually a treaty is a deal about peace or trade.) 

The treaties were between the Americans and the native people who lived out West.  The President at the time was Thomas Jefferson.

In 1803, the U.S. bought thousands of square miles of land from France.  This land was called the Louisiana Purchase.  President Jefferson wanted to give away some of the land.  He wanted to offer it to native peoples who lived east of the Mississippi.  But they would have to give away their homelands.  They would have to move out West.