, ▁Mont ana . ▁North ▁of ▁Hel ena , ▁the ▁road ▁left ▁the ▁Missouri ▁and ▁followed ▁Ten mile ▁Creek ▁and ▁Austin ▁Creek ▁up ▁to ▁M ull an ▁Pass , ▁where ▁it ▁crossed ▁the ▁Cont inental ▁Div ide . ▁In ▁ 1 8 6 6 , ▁the ▁Little ▁Pr ick ly ▁Pear ▁W agon ▁Road ▁Company ▁secured ▁a ▁license ▁to ▁manage ▁the ▁M ull an ▁Road ▁from ▁Craig ▁to ▁Hel ena , ▁and ▁made ▁significant ▁improvements ▁to ▁it . ▁ ▁In ▁ 1 8 7 2 , ▁engineer ▁Thomas ▁Roberts ▁survey ed ▁the ▁valley ▁for ▁the ▁Northern ▁Pacific ▁Railway . ▁Roberts ▁recommended ▁that ▁the ▁railway ▁ship ▁goods ▁via ▁steam ship ▁through ▁the ▁can y on ▁rather ▁than ▁by ▁rail road . ▁The ▁plan ▁was ▁not ▁acted ▁on . ▁Two ▁years ▁later , ▁however , ▁the ▁rail road ▁contract ed ▁with ▁the ▁Diam ond ▁R ▁Fre ight ▁Company ▁to ▁build ▁a ▁w agon ▁road ▁from ▁Hel ena ▁through ▁the ▁can y on ▁past ▁Tower ▁Rock ▁to ▁the ▁new ▁trad ing ▁post ▁of ▁Car roll ▁at ▁the ▁head w aters ▁of ▁the ▁M uss el shell ▁River . ▁The ▁" Car roll ▁Tra il " ▁was ▁constructed , ▁but ▁closed ▁in ▁ 1 8 7 6 ▁due ▁to ▁host ility ▁from ▁Native ▁Americans ▁and ▁sh ifts ▁in ▁the ▁Missouri ▁River ' s ▁channel . ▁In ▁ 1 8 8 5 , ▁the ▁St . ▁Paul , ▁Min ne apolis ▁& ▁Man it oba ▁Railway ▁( which ▁later ▁became ▁part ▁of ▁the ▁Great ▁Northern ▁Railway ) ▁decided