US 93 enters Montana from Idaho at Lost Trail Pass and travels north descending through the Bitterroot National Forest. The highway continues along the Lewis and Clark Trail into the Bitterroot Valley toward Missoula, passing through Darby and Hamilton. At Lolo, US 12 joins from the west and they run concurrently northeasterly for , where US 93 heads due north on Reserve Street in Missoula. US 93 then joins I-90 and runs concurrently westward for to Wye, where it heads north.