According to the 2000 census , the county has a total area of 591.90 square miles ( 1,533.0 km2 ) , of which 569.35 square miles ( 1,474.6 km2 ) ( or 96.19 % ) is land and 22.55 square miles ( 58.4 km2 ) ( or 3.81 % ) is water .
Of this , 569.35 square miles ( 1,474.6 km2 ) ( or 96.19 % ) is land and 22.55 square miles ( 58.4 km2 ) ( or 3.81 % ) is water .