In the period between 1995 and 1999, there was no numbered speed limit on I-90 in Montana. The speed limit was simply defined as reasonable and prudent as determined on a case-by-case basis by the Montana Highway Patrol. The speed limit in Montana is now . From the west I-90 enters Montana on the summit of Lookout Pass. It passes next to Missoula and runs through Butte, where it connects with I-15 for close to , before crossing the continental divide just east of Butte where it goes over Homestake Pass, which is in elevation, the highest point for the Interstate.