owa   5 1 ) ▁is ▁a ▁state ▁highway ▁that ▁runs ▁from ▁north ▁to ▁south ▁in ▁n ortheast ▁Iowa . ▁Cont ained ▁entirely ▁by ▁All am ake e ▁County , ▁it ▁is ▁only ▁ ▁in ▁length . ▁ ▁It ▁begins ▁at ▁U . S . ▁Highway ▁ 1 8 ▁( US   1 8 ) ▁and ▁US   5 2 ▁in ▁Post ville ▁and ▁ends ▁at ▁Iowa ▁ 9 ▁near ▁W au kon . ▁ ▁Route ▁description ▁ ▁Iowa ▁ 5 1 ▁begins ▁at ▁the ▁intersection ▁of ▁T ild en ▁and ▁Law ler ▁Stre ets ▁in ▁Post ville . ▁US ▁ 1 8 ▁and ▁US ▁ 5 2 ▁form ▁the ▁southern ▁and ▁western ▁for ks ▁of ▁the ▁intersection , ▁T ild en ▁Street ▁continues ▁east , ▁and ▁Iowa ▁ 5 1 ▁begins ▁heading ▁north ▁along ▁Law ler ▁Street ▁through ▁Post ville ' s ▁dow nt own ▁area . ▁ ▁The ▁highway ▁cross es ▁a ▁line ▁of ▁the ▁Dak ota , ▁Minnesota ▁and ▁Eastern ▁Rail road ▁and ▁leaves ▁Post ville ▁heading ▁in ▁an ▁almost ▁directly ▁north ward ▁alignment . ▁The ▁only ▁curves ▁along ▁the ▁route ▁come ▁as ▁the ▁highway ▁desc ends ▁into ▁and ▁then ▁asc ends ▁out ▁of ▁the ▁Y ellow ▁River ▁valley . ▁ ▁Between ▁W au kon ▁and ▁Dec or ah , ▁the ▁route ▁termin ates ▁at ▁an ▁intersection ▁with ▁Iowa ▁ 9 . ▁ ▁History ▁When ▁it ▁was ▁originally ▁designated , ▁Iowa ▁ 5 1 ▁was ▁not ▁a ▁p aved ▁highway . ▁The ▁route ▁was ▁fully ▁p aved ▁by ▁ 1