▁through ▁Miss ou la ' s ▁dow nt own , ▁eventually ▁meeting ▁I - 9 0 . ▁It ▁then ▁over laps ▁I - 9 0 ▁for ▁, ▁until ▁G arrison , ▁where ▁it ▁heads ▁east ▁toward ▁Hel ena ▁for ▁. ▁This ▁two - lane ▁section ▁of ▁the ▁trip ▁passes ▁through ▁Av on ▁and ▁Ell ist on ▁w inding ▁through ▁the ▁Hel ena ▁National ▁Forest , ▁over ▁the ▁Cont inental ▁Div ide ▁at ▁Mac Donald ▁Pass , ▁and ▁then ▁through ▁Mont ana ' s ▁capital ▁city , ▁Hel ena . ▁ ▁US   1 2 ▁passes ▁over ▁Inter state ▁ 1 5 ▁at ▁which , ▁point ▁it ▁joins ▁US   2 8 7 ▁south . ▁US   1 2 ▁over laps ▁US   2 8 7 ▁and ▁heads ▁sout heast , ▁toward ▁Town send ▁for ▁, ▁where ▁it ▁spl its ▁from ▁US   2 8 7 , ▁which ▁heads ▁south ▁for ▁ ▁toward ▁the ▁intersection ▁of ▁I - 9 0 ▁near ▁the ▁town ▁of ▁Three ▁F ork s . ▁US   1 2 ▁heads ▁east ▁toward ▁White ▁Sul ph ur ▁Spr ings ▁for ▁. ▁The ▁route ▁joins ▁US   8 9 ▁for ▁ ▁before ▁entering ▁White ▁Sul ph ur ▁Spr ings , ▁and ▁for ▁another ▁ ▁east ▁of ▁town . ▁US   8 9 ▁spl its ▁north ▁and ▁US   1 2 ▁continues ▁east ▁on ▁its ▁own ▁for ▁, ▁until ▁the ▁j unction ▁with ▁I - 9 4 ▁at ▁F ors yth ▁as ▁a ▁conc urrency ▁n ortheast ▁for ▁, ▁to ▁Mil es ▁City