▁( 0 . 1 %) ▁is ▁water . ▁It ▁is ▁the ▁fourth - larg est ▁county ▁by ▁area ▁in ▁Iowa . ▁ ▁Ad j acent ▁count ies ▁ ▁Si oux ▁County ▁ ▁( n orth ) ▁ ▁Ch ero kee ▁County ▁ ▁( east ) ▁ ▁Wood bury ▁County ▁ ▁( s outh ) ▁ ▁Union ▁County , ▁South ▁Dak ota ▁ ▁( west ) ▁ ▁Transport ation ▁ ▁Major ▁high ways ▁▁ ▁U . S . ▁Highway ▁ 7 5 ▁▁ ▁Iowa ▁Highway ▁ 3 ▁▁ ▁Iowa ▁Highway ▁ 1 2 ▁▁ ▁Iowa ▁Highway ▁ 6 0 ▁▁ ▁Iowa ▁Highway ▁ 1 4 0 ▁ ▁Airport ▁Le ▁Mars ▁Municipal ▁Airport ▁is ▁located ▁in ▁P ly mouth ▁County , ▁two ▁na ut ical ▁miles ▁( 3 . 7   km ) ▁south west ▁of ▁the ▁central ▁business ▁district ▁of ▁Le ▁Mars . ▁ ▁Dem ograph ics ▁▁ 2 0 1 0 ▁census ▁The ▁ 2 0 1 0 ▁census ▁recorded ▁a ▁population ▁of ▁ 2 4 , 9 8 6 ▁in ▁the ▁county , ▁with ▁a ▁population ▁density ▁of ▁. ▁There ▁were ▁ 1 0 , 5 5 0 ▁housing ▁units , ▁of ▁which ▁ 9 , 8 7 5 ▁were ▁occupied . ▁▁ 2 0 0 0 ▁census ▁ ▁As ▁of ▁the ▁census ▁of ▁ 2 0 0 0 , ▁there ▁were ▁ 2 4 , 8 4 9 ▁people , ▁ 9 , 3 7 2 ▁households , ▁and ▁ 6 , 8 0 4 ▁families ▁in ▁the ▁county . ▁The