MTMontana Geography

Snow that melts off Triple Divide Peak in Glacier National Park can finish in three different oceans. The 8,020 foot summit is the one place in North America where the Continental Divide meets the Laurentian Divide, so water leaving its slopes reaches the Pacific by the Flathead and Columbia, the Gulf of Mexico by the Missouri and Mississippi, and Hudson Bay by the Saint Mary and the Nelson. That single hydrological knot is why the Glacier country gets called the Crown of the Continent, and it is the most useful fact to hold onto when reading a map of Montana.

Three oceans from one summit

The Continental Divide enters Montana from Alberta in Glacier National Park, runs southeast past Helena and Butte, then doubles back west and south along the crest of the Bitterroot Range to Yellowstone. Because of that hook, Butte sits on the Divide while Missoula, well to the west, drains to the Pacific and Billings, to the east, drains to the Gulf.

Marias Pass, at 5,213 feet, is the lowest crossing of the Divide in the northern Rockies. A Great Northern Railway surveyor named John F. Stevens located it on snowshoes in December 1889 after the company had spent years looking for a way through, and the railroad went over it in 1891. US 2 follows the same gap today, which is why the only highway along the southern edge of Glacier National Park sits at an elevation lower than downtown Denver.

Granite Peak, the last state summit to be climbed

Montana's high point is Granite Peak, 12,807 feet, in the Beartooth Mountains of Park County. It is invisible from any road, guarded by a long approach and a final scramble on exposed rock, and it was not summited until 1923, making it the last of the fifty state high points to record a first ascent. The party included Elers Koch, a Forest Service officer who had already tried and failed twice.

The low point is the Kootenai River at 1,800 feet, where it crosses into Idaho in the far northwest corner of Lincoln County. The 11,007 foot spread between the two is one of the widest of any state.

Around Granite Peak, the Beartooth Plateau carries more than twenty named summits above 12,000 feet and holds the largest continuous expanse of land above 10,000 feet in the contiguous United States. The Beartooth Highway crosses it at 10,947 feet, and snow keeps the road shut for roughly half the year.

Where the Rockies end in a wall

Along a north to south line from Glacier National Park past Choteau and Augusta, the mountains stop without foothills. This is the Rocky Mountain Front, the leading edge of the Lewis Overthrust, where a sheet of Precambrian rock roughly 1.5 billion years old was shoved eastward over Cretaceous shale a fraction of its age. Chief Mountain, 9,085 feet, stands out on the prairie as a detached remnant of that sheet, old rock sitting on much younger rock with nothing connecting it to the range behind.

East of the Front, the Great Plains take up roughly three fifths of Montana. They are not featureless. Isolated island ranges push out of the grass, the Bears Paw, the Little Rocky, the Judith, the Highwood, the Big Snowy and the Sweet Grass Hills, all built from igneous intrusions with no structural link to the Rockies. Further east, near Glendive, Makoshika State Park cuts into the Hell Creek Formation, the badlands where Barnum Brown found the first Tyrannosaurus rex skeleton in 1902.

Rivers, and 545 miles of the 49th parallel

The Missouri River begins in Montana, at Three Forks, where the Jefferson, Madison and Gallatin come together. Lewis and Clark named all three in July 1805 and treated the junction as the head of the river. The Yellowstone runs 692 miles from Wyoming across southern Montana without a single dam on its main stem, the longest free-flowing river left in the lower forty-eight, and joins the Missouri just past the North Dakota line.

Fort Peck Dam, built between 1933 and 1940, stretches 21,026 feet across the Missouri and backs up a reservoir with about 1,520 miles of shoreline. In the west, Flathead Lake covers roughly 191 square miles, the largest natural freshwater lake west of the Mississippi in the contiguous states.

Montana's northern boundary follows the 49th parallel for about 545 miles, the longest Canadian border of any state outside Alaska, and it touches British Columbia, Alberta and Saskatchewan. No other state borders three provinces. The western boundary is the opposite of a survey line: from the Canadian border it drops south along a meridian, then bends and follows the crest of the Bitterroot Range and the Continental Divide, one of very few state lines in the country drawn along a watershed rather than a compass bearing.

The coldest reading in the contiguous states

On 20 January 1954 a mining camp at Rogers Pass in Lewis and Clark County recorded minus 70 degrees Fahrenheit, still the lowest temperature ever measured in the contiguous United States. At the other end, Montana has touched 117 degrees, at Glendive in July 1893 and Medicine Lake in July 1937.

The swings between those extremes are just as distinctive. On 14 and 15 January 1972, Loma went from minus 54 to 49 degrees in twenty-four hours, a 103 degree change and the largest ever recorded in the country. Chinook winds pouring off the Rocky Mountain Front, compressed and warmed as they drop onto the plains, do that repeatedly through a Montana winter. In Glacier National Park, 26 named glaciers remain of roughly 150 counted in 1850.

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