 Harrison County 's surface is covered by many hills and valleys . The Knobstone Escarpment begins in the southeastern part of the county , rising sharply at the Ohio River , and following a course roughly along the eastern edge of the county . The " knobs " are the most significant series of hills in Indiana , with the highest knobs near the Ohio River towering 610 feet ( 190 m ) over the surrounding valley . This is the greatest local relief difference in the state . The Ohio River borders the entire southeastern , southern , and southwestern part of the county . Blue River forms the western border with Indian Creek and Buck Creek as the primary internal drainage systems . 
