Montana has more highway than almost anything else — the longest stretch of I-90 in any state, the Hi-Line running the top of the country, and hundred-mile gaps where your phone has no bars at all. All of it runs on mile markers. Here's how they work across Big Sky Country, where they matter most, and how to see your exact one plus live Montana 511 conditions in real time.

How Montana numbers its highways

Montana's mileposts count up from where a route enters the state on its west or south side — I-90 starts at mile 0 on the Idaho line at Lookout Pass and doesn't run out until the Wyoming line around mile 552. That's the longest run of I-90 in any state, and it's why a milepost is the only sane way to describe a location out here: "I-90 at milepost 381" means something; "east of Bozeman" could be a hundred miles. Mile marker data for every Montana highway — all 358 routes, including MT-200, the longest state highway in America — is bundled into the app and works offline.

The corridors people actually drive

  • I-90 crosses the whole state — Lookout Pass, Missoula, Butte, Bozeman, Billings — about 552 miles.
  • I-15 runs south-north from Monida Pass through Butte, Helena, and Great Falls to the Canadian border.
  • I-94 splits off at Billings and heads for North Dakota through Miles City and Glendive.
  • US-2 is the Hi-Line — the long northern route past Glacier; US-93 runs the Bitterroot and Flathead valleys; MT-200 crosses virtually the entire state.

Where mile markers matter most: the passes and the gaps

Homestake Pass, just east of Butte around milepost 233, is the highest point on all of I-90 — 6,329 feet, crossing the Continental Divide, icy for a good share of the year. Lookout Pass at the Idaho line and Bozeman Pass east of town see the same winter. But Montana's other defining feature is emptiness: stretches where the next town — and the next cell bar — is an hour away. When something goes wrong out there, the milepost is the only address you have.

MP 0 · Idaho line MP 200 MP 552 · Wyoming line Missoula Bozeman Billings Homestake Pass · MP 233
I-90 crosses Montana from Lookout Pass on the Idaho line to Wyoming near mile 552 — over Homestake Pass at milepost 233, the highest point on I-90 anywhere in America.

Winter, wind, and the Beartooth

Montana's most famous closure is seasonal: the Beartooth Highway on US-212, the switchback climb to nearly 11,000 feet southwest of Red Lodge, closes every fall and doesn't reopen until late spring. In winter, the interstates earn their reputation — black ice on the passes, ground blizzards on the Hi-Line where wind erases the road, and chain requirements that arrive fast. Every closure and condition is announced by milepost, and out here the alert often matters more than the forecast.

Live Montana 511 alerts, in one place

MileCheck pulls live road alerts straight from Montana's 511 system: closures, crashes, construction, and winter road conditions, tied to the mile marker and direction so you can see what's ahead of you on your route — before you're forty miles past the last exit that could have saved you the trip.

Everyday and emergency

Whether you're crossing the Divide at Homestake in January, running the Hi-Line where towns are an hour apart, or reporting a breakdown where there's no signal at all, the mile marker is the location Montana's roads run on. MileCheck shows yours in real time, down to a tenth of a mile — and because the data is stored on your phone, it works exactly where the bars don't.

Keep reading

Nearby state guides: Idaho  ·  North Dakota  ·  South Dakota  ·  Wyoming

Essentials: What to tell 911 on the highway  ·  How to find your mile marker  ·  Browse the live mile marker map  ·  All 50 states