The state of Mississippi joined the Union on December 10, 1817. Prior to that, it was the western part of the Mississippi Territory.
The western boundary of the state is the Mississippi River, which has a habit of shifting all over the place as it wiggles south. If Rhinos cared much about where We are, this could get confusing.
A Rhino Tip: always keep an eye on rivers; they are seldom exactly where you left them.