sentences:  According to the U.S. Census Bureau, the county has a total area of , of which is land and (3.3%) is water.The western part of the county on the Mississippi River is part of the American Bottom floodplain, while the eastern portion of the county is relatively flat and was originally prairie.The transition zone between has high bluffs of limestone and dolomite and has distinctive Karst topography with numerous sinkholes, caves, and springs.