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Mason County


mason county map Map legend and scale


Low elevation: <435 feet above mean sea level
      Place: Illinois River
      7.5' quadrangle name: Clear Lake
      PLSS: 3-5-19N-11W
      Geology: Cahokia Alluvium in river valley

High elevation: >730 feet above mean sea level
      Place: 2 unnamed hills along a ridge
      7.5' quadrangle name: Easton
      PLSS: 3-25-20N-7W
      Geology: Parkland sand ridges (esker?)

Area: 557.44 square miles
      Total relief (approximate): 295 feet
      Average percent slope: 0.54%


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Updated 5/4/2007 JKH