According to the U.S. Census Bureau , the county has a total area of 6,136 square miles ( 15,892.2 km2 ) , of which 5,944 square miles ( 15,394.9 km2 ) is land and 192 square miles ( 497.3 km2 ) ( 3.12 % ) is water .
5,944 square miles ( 15,394.9 km2 ) is land and 192 square miles ( 497.3 km2 ) ( 3.12 % ) is water .