. ▁At ▁the ▁east ▁exit ▁for ▁Mil es ▁City , ▁US   1 2 ▁spl its ▁again ▁from ▁I - 9 4 ▁and ▁heads ▁almost ▁directly ▁east ▁to ▁the ▁North ▁Dak ota ▁border ▁at ▁a ▁distance ▁of ▁. ▁ ▁North ▁Dak ota ▁ ▁US ▁ 1 2 ▁is ▁a ▁two - lane ▁und iv ided ▁highway ▁that ▁runs ▁, ▁through ▁Adams , ▁Bow man ▁and ▁Slo pe ▁count ies ▁in ▁south west ▁North ▁Dak ota . ▁ ▁The ▁speed ▁limit ▁is ▁ ▁on ▁rural ▁segments , ▁with ▁slower ▁posted ▁spe eds ▁within ▁the ▁cities ▁of ▁Mar mar th , ▁Rh ame , ▁Bow man , ▁Sc r anton ▁and ▁Het ting er . ▁US ▁ 1 2 ▁meets ▁with ▁US ▁ 8 5 ▁in ▁Bow man , ▁and ▁the ▁routes ▁are ▁concurrent ▁for ▁a ▁short ▁distance ▁through ▁the ▁city . ▁ ▁South ▁Dak ota ▁US ▁ 1 2 ▁enters ▁South ▁Dak ota ▁from ▁North ▁Dak ota ▁as ▁a ▁rural ▁two ▁l ane ▁highway ▁about ▁ ▁west / n orth west ▁of ▁Lem mon ▁before ▁entering ▁the ▁Stand ing ▁Rock ▁Res ervation . ▁ ▁For ▁approximately ▁the ▁next ▁, ▁US ▁ 1 2 ▁runs ▁parallel ▁to ▁the ▁border ▁of ▁North ▁Dak ota , ▁sometimes ▁within ▁less ▁than ▁a ▁mile . ▁ ▁At ▁Walker , ▁US ▁ 1 2 ▁heads ▁sout heast ▁for ▁, ▁where ▁it ▁cross es ▁the ▁Missouri ▁River ▁at ▁M ob ridge , ▁exit ing ▁the ▁res ervation . ▁ ▁From ▁there ▁it ▁continues ▁east ▁for ▁, ▁until ▁it ▁meets ▁with ▁US