US 93 enters Montana from Idaho at Lost Trail Pass and travels north descending through the Bitterroot National Forest.

At Lolo, US 12 joins from the west and they run concurrently northeasterly for 7.5 miles (12.1 km), where US 93 heads due north on Reserve Street in Missoula.

From Wye, US 93 continues north through the Flathead Indian Reservation, where its signage includes the historic Salish and Kutenai names for towns, rivers, and streams.

Many stretches have been widened and straightened, or else rerouted in ongoing efforts to improve traffic safety and preserve animals at the same time.

[6] With concern for the nearby designated wilderness and grizzly bear habitat in the Mission Mountains, an agreement with the state and the Federal Highway Administration was reached in December 2000.