The topography of the Arkansas River Valley in the vicinity of the fort is gently sloping.  The bedrock is Bridge Creek Limestone, a member of the Greenhorn Limestone Formation.  The river valley has quarternary alluvium deposits from the Wisconsin age that is overlaid with recent alluvial deposits.  The museum collection has several examples of fossils.  The region has a potential for oil and minerals but to date no exploration or development is planned.

- August 26th, 1870, Peter G. Scott describes in his diary the river and its banks outside the fort. 
--"It runs quite rapidly, is clear and has a fringe of . . trees along its banks most places and a narrow strip of green grass, behind which rise sand bluffs."