Montana is a state in the Mountain West region of the United States. It is bordered by Idaho to the west; North Dakota and South Dakota to the east; Wyoming to the south; and by the Canadian provinces of Alberta, British Columbia, and Saskatchewan to the north. It is the fourth-largest state by area, the eighth-least populous state, and the third-least densely populated state. The western half of Montana contains numerous mountain ranges, while the eastern half is characterized by western prairie terrain and badlands, with more (albeit smaller) mountain ranges found throughout the state. In all, 77 named ranges are part of the Rocky Mountains.
Montana has no official nickname but several unofficial ones, most notably "Big Sky Country", "The Treasure State", "Land of the Shining Mountains", and "The Last Best Place". The economy is primarily based on agriculture, including ranching and cereal grain farming. Other significant economic resources include oil, gas, coal, mining, and lumber. The health care, service, and government sectors also are significant to the state's economy. Montana's fastest-growing sector is tourism; nearly 13 million annual tourists visit Glacier National Park, Yellowstone National Park, Beartooth Highway, Flathead Lake, Big Sky Resort, and other attractions.
With an area of 147,040 square miles (380,800 squre kilometres), Montana is slightly larger than Japan. It is the fourth-largest state in the United States after Alaska, Texas, and California; it is the largest landlocked state.
The state's topography is roughly defined by the Continental Divide, which splits much of the state into distinct eastern and western regions. Most of Montana's hundred or more named mountain ranges are in the state's western half, most of which is geologically and geographically part of the northern Rocky Mountains. The Absaroka and Beartooth ranges in the state's south-central part are technically part of the Central Rocky Mountains. The Rocky Mountain Front is a significant feature in the state's north-central portion, and isolated island ranges that interrupt the prairie landscape common in the central and eastern parts of the state. About 60 percent of the state is prairie, part of the northern Great Plains.
The Bitterroot Mountains — one of the longest continuous ranges in the Rocky Mountain chain from Alaska to Mexico — along with smaller ranges, including the Coeur d'Alene Mountains and the Cabinet Mountains, divide the state from Idaho. The southern third of the Bitterroot range blends into the Continental Divide. Other major mountain ranges west of the divide include the Cabinet Mountains, the Anaconda Range, the Missions, the Garnet Range, the Sapphire Mountains, and the Flint Creek Range.
The divide's northern section, where the mountains rapidly give way to prairie, is part of the Rocky Mountain Front. The front is most pronounced in the Lewis Range, located primarily in Glacier National Park. Due to the configuration of mountain ranges in Glacier National Park, the Northern Divide (which begins in Alaska's Seward Peninsula) crosses this region and turns east in Montana at Triple Divide Peak. It causes the Waterton River, Belly, and Saint Mary rivers to flow north into Alberta, Canada. There they join the Saskatchewan River, which ultimately empties into Hudson Bay.
East of the divide, several roughly parallel ranges cover the state's southern part, including the Gravelly Range, Madison Range, Gallatin Range, Absaroka Mountains, and Beartooth Mountains. The Beartooth Plateau is the largest continuous land mass over 10,000 feet (3,000 m) high in the continental United States. It contains the state's highest point, Granite Peak, 12,799 feet (3,901 m) high. North of these ranges are the Big Belt Mountains, Bridger Mountains, Tobacco Roots, and several island ranges, including the Crazy Mountains and Little Belt Mountains.
Between many mountain ranges are rich river valleys. The Big Hole Valley, Bitterroot Valley, Gallatin Valley, Flathead Valley, and Paradise Valley have extensive agricultural resources and multiple opportunities for tourism and recreation.
East and north of this transition zone are the expansive and sparsely populated Northern Plains, with tableland prairies, smaller island mountain ranges, and badlands. The isolated island ranges east of the Divide include the Bear Paw Mountains, Bull Mountains, Castle Mountains, Crazy Mountains, Highwood Mountains, Judith Mountains, Little Belt Mountains, Little Rocky Mountains, the Pryor Mountains, Little Snowy Mountains, Big Snowy Mountains, Sweet Grass Hills, and — in the state's southeastern corner near Ekalaka — the Long Pines. Many of these isolated eastern ranges were created about 120 to 66 million years ago when magma welling up from the interior cracked and bowed the earth's surface here.
The area east of the divide in the state' north-central portion is known for the Missouri Breaks and other significant rock formations. Three buttes south of Great Falls are major landmarks: Cascade, Crown, Square, Shaw, and Buttes. Known as laccoliths, they formed when igneous rock protruded through cracks in the sedimentary rock. The underlying surface consists of sandstone and shale. Surface soils in the area are highly diverse, and greatly affected by the local geology, whether glaciated plain, intermountain basin, mountain foothills, or tableland. Foothill regions are often covered in weathered stone or broken slate, or consist of uncovered bare rock (usually igneous, quartzite, sandstone, or shale). The soil of intermountain basins usually consists of clay, gravel, sand, silt, and volcanic ash, much of it laid down by lakes which covered the region during the Oligocene 33 to 23 million years ago. Tablelands are often topped with argillite gravel and weathered quartzite, occasionally underlain by shale. The glaciated plains are generally covered in clay, gravel, sand, and silt left by the proglacial Lake Great Falls or by moraines or gravel-covered former lake basins left by the Wisconsin glaciation 85,000 to 11,000 years ago. Farther east, areas such as Makoshika State Park near Glendive and Medicine Rocks State Park near Ekalaka contain some of the most scenic badlands regions in the state.
The Hell Creek Formation in Northeast Montana is a major source of dinosaur fossils. Paleontologist Jack Horner of the Museum of the Rockies in Bozeman brought this formation to the world's attention with several major finds.
