▁ ▁US ▁ 1 2 ▁is ▁now ▁the ▁only ▁U . S . ▁Highway ▁still ▁serving ▁dow nt own ▁Detroit , ▁whose ▁street ▁grid ▁was ▁laid ▁by ▁August us ▁B . ▁Wood ward , ▁to ▁have ▁a ▁five - way ▁intersection ▁of ▁the ▁roads ▁that ▁would ▁become ▁US ▁ 1 2 , ▁US ▁ 1 0 , ▁US ▁ 1 6 , ▁US ▁ 1 1 2 ▁and ▁US ▁ 2 5 . ▁US ▁ 2 4 ▁still ▁travel s ▁through ▁Detroit ▁from ▁Pur itan ▁to ▁ 8 ▁M ile ▁Road ▁on ▁the ▁far ▁west ▁side . ▁ ▁As ▁from ▁the ▁earliest ▁days ▁of ▁its ▁existence , ▁US ▁ 1 2 ▁enters ▁Michigan ▁from ▁Indiana , ▁south west ▁of ▁New ▁Buff alo ▁and ▁continues ▁to ▁the ▁old ▁j unction ▁of ▁US ▁ 1 2 ▁and ▁US ▁ 1 1 2 ▁in ▁New ▁Buff alo . ▁It ▁is ▁now ▁assigned ▁between ▁New ▁Buff alo ▁and ▁Detroit ▁( except ▁through ▁Y ps il anti ), ▁along ▁what ▁was ▁US ▁ 1 1 2 ▁until ▁ 1 9 6 2 . ▁ ▁On ▁May ▁ 4 , ▁ 2 0 0 4 , ▁the ▁Michigan ▁Department ▁of ▁Transport ation ▁( MD OT ) ▁designated ▁ ▁of ▁US ▁ 1 2 ▁from ▁New ▁Buff alo ▁to ▁Detroit ▁as ▁a ▁Historic ▁Heritage ▁Route . ▁The ▁east - west ▁cor rid or ▁travers es ▁the ▁count ies ▁of ▁Ber rien , ▁Cass , ▁St . ▁Joseph , ▁Branch , ▁Hill sd ale , ▁L ena we e , ▁Was