The river forms most of Arkansas's eastern border
The area is also 
home to a rich biodiversity and contains one of the most fertile lands in the... [DOC] [TLE] Arkansas State Boundaries - Encyclopedia of Arkansas [PAR] Apr 28, 2010 ... As a result, Arkansas's southern boundary was established at ... will be left to the 
South to form the territory of Arkansas, with the River Arkansas... [DOC] [TLE] What river is a natural feature that forms Arkansas eastern border [PAR] The Mississippi river.