The topography of the state is diverse, but roughly defined by the Continental Divide, which runs on an approximate diagonal through the state from northwest to south-central, splitting it into two distinct eastern and western regions. Montana is well known for its mountainous western region, part of the northern Rocky Mountains. However, about 60% of the state is actually prairie, part of the northern Great Plains. Nonetheless, even east of the Continental Divide and the Rocky Mountain Front, there are a number of isolated "Island Ranges" that dot the prairie landscape. The entire state contains approximately 77 named mountain ranges.

St. Mary's Lake in Glacier National ParkThe Bitterroot Mountains, divide the state from Idaho to the west with the southern third of the range blending into the Continental Divide. Mountain ranges between the Bitterroots and the top of the Continental Divide include the Cabinet Mountains, the Missions, the Garnet, Sapphire, Flint Creek, and Pintlar ranges.

The northern section of the Divide, where the mountains give way rapidly to prairie, is known collectively as the Rocky Mountain Front and 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 the Seward Peninsula) crosses this region and turns east in Montana at Triple Divide Peak. Thus, the Waterton, Belly, and Saint Mary Rivers flow north into Alberta, Canada joining the Saskatchewan River, and ultimately emptying into Hudson Bay.

East of the Divide, several parallel ranges march across the southern half of the state, including the Gravelly Range, the Tobacco Roots, the Madison Range, Gallatin Range, Big Belt Mountains, Bridger Mountains, Absaroka Mountains and the Beartooth Mountains. The Beartooth Plateau is the largest continuous land mass over 10,000 feet (3,000 m) in the lower 48 states and contains the highest point in the state, Granite Peak, 12,799 feet (3,901 m) high.

Between the Mountain ranges are many scenic valleys, rich in agricultural resources, rivers and possessing multiple opportunities for tourism and recreation. Among the best-known areas are the Flathead Valley, Bitterroot Valley, Big Hole Valley, and Gallatin Valley.

Pompeys Pillar National Monument East and north of this transition zone are expansive sparsely populated Northern Plains, with rolling tableland prairies, "island" mountain ranges, and scenic badlands extending into the Dakotas, Alberta, Saskatchewan and Wyoming. The isolated "Island" ranges east of the Divide include the Castle Mountains, Crazy Mountains, Little Belt Mountains, Snowy Mountains, Sweet Grass Hills, Bull Mountains and, in the southeastern corner of the state near Ekalaka, the Long Pines and Short Pines.

The area east of the divide in the north-central portion of the state is known for the dramatic Missouri Breaks and other significant rock formations. Three stately buttes south of Great Falls are familiar landmarks. These buttes, Square Butte, Shaw Butte, and Crown Butte, are made of igneous rock, which is dense and has withstood weathering for many years. The underlying surface consists of shale. Many areas around these buttes are covered with clay surface soils. These soils have been derived from the weathering of the Colorado Formation. Farther east, areas such as Makoshika State Park near Glendive, and Medicine Rocks State Park near Ekalaka also highlight some of the most scenic badlands regions in the state.

Montana also contains a number of rivers, many of which are known for "blue-ribbon" trout fishing, but which also provide most of the water needed by residents of the state, as well as being a source of hydropower. Montana is the only state in the union whose rivers form parts of three major North American watersheds: The Pacific Ocean, the Gulf of Mexico, and Hudson Bay which are divided atop Triple Divide Peak in Glacier National Park.

West of the divide, the Clark Fork of the Columbia (not to be confused with the Clarks Fork of the Yellowstone River) rises in the Rocky Mountains near Butte, flows west toward Missoula where it is joined by the Blackfoot River and the Bitterroot River and turns to the northwest, entering Idaho just above Lake Pend Oreille, becoming part of the Columbia River, which flows to the Pacific Ocean. The Clark Fork discharges the greatest volume of water of any river exiting the state. The Flathead River and Kootenai River also drain major portions of the western half of the state.

East of the divide, the Missouri River, formed by the confluence of the Jefferson, Madison and Gallatin rivers, crosses the central part of the state, flows through the Missouri breaks and enters North Dakota. The Yellowstone River rises in Yellowstone Park in Wyoming, flows north to Livingston, Montana, where it then turns east and flows across the state until it joins the Missouri River a few miles east of the North Dakota boundary. The Yellowstone River is the longest undammed, free-flowing river in North America. Other major Montana tributaries of the Missouri include the Milk, Marias, Tongue, and Musselshell Rivers. Montana also claims the disputed title of possessing the "world's shortest river", the Roe River, just outside Great Falls, Montana. These rivers ultimately join the Mississippi River and flow into the Gulf of Mexico.

Water is of critical importance to the state for both agriculture and hydropower. In addition to its rivers, the state is home to Flathead Lake, the largest natural fresh-water lake west of the Great Lakes. Man-made reservoirs dot Montana's rivers, the largest of which is Fort Peck Reservoir, on the Missouri river, contained by the largest earth-filled dam in the world.

Vegetation of the state includes ponderosa pine, lodgepole pine, larch, fir, spruce, aspen, birch, red cedar, ash, alder, rocky mountain maple and cottonwood trees. Forests cover approximately 25% of the state. Flowers native to Montana include asters, bitterroots, daisies, lupins, poppies, primroses, columbine, lilies, orchids and dryads. Several species of sagebrush and cactus and many species of grasses are common. Many species of mushrooms and lichens are also found in the state.

Montana contains Glacier National Park and portions of Yellowstone National Park, including three of the Park's five entrances. Other federally recognized sites include the Little Bighorn National Monument, Bighorn Canyon National Recreation Area, Big Hole National Battlefield, Lewis and Clark Caverns, and the National Bison Range. Montana has eight National Forests and over 20 National Wildlife Refuges. The Federal government administers 36,000,000 acres (146,000 km²). 275,000 acres (1,100 km²) are administered as state parks and forests.

Subsequent to the Lewis and Clark expedition and after the finding of gold and copper (see the Copper Kings) in the state in the late 1850s, Montana became a United States territory (Montana Territory) on May 26, 1864 and the 41st state on November 8, 1889.

Fort Shaw (Montana Territory) was established in the spring of 1867. It is located west of Great Falls in the Sun River Valley and was one of three posts authorized to be built by Congress in 1865. The other two posts in the Montana Territory were Camp Cooke on the Judith River and Fort C.F. Smith on the Bozeman Trail in south central Montana Territory. Fort Shaw, named after Colonel Robert Gould Shaw, who commanded the 54th Massachusetts, one of the first all African-American regiments, during the American Civil War, was built of adobe and lumber by the 13th Infantry. The fort had a parade ground that was 400 ft² (120 m²), and consisted of barracks for officers, a hospital, and a trading post, and could house up to 450 soldiers. Completed in 1868, it was used by military personnel until 1891.

After the close of the military post, the government established Fort Shaw as a school to provide industrial training to young Native Americans. The Fort Shaw Indian Industrial School was opened on April 30, 1892. The school had at one time 17 faculty members, 11 Indian assistants and 300 students. The school made use of over 20 of the buildings built by the Army.

The revised Homestead Act of the early 1900s greatly affected the settlement of Montana. This act expanded the land that was provided by the Homestead Act of 1862 from 160 acres to 320 acres (65-130 ha). When the latter act was signed by President Taft, it also reduced the time necessary to prove up from five years to three years and permitted five months absence from the claim each year.

In 1908, the Sun River Irrigation Project, west of Great Falls was opened up for homesteading. Under this Reclamation Act, a person could obtain 40 acres (16 ha). Most of the people who came to file on these homesteads were young couples who were eager to live near the mountains where hunting and fishing were good. Many of these homesteaders came from the Midwest and Minnesota.

Montana was the scene of the Native Americans' last effort to keep their land, and the last stand of U.S. Army Lieutenant Colonel George Armstrong Custer was fought near the present day town of Hardin. Montana was also the location of the final battles of the Nez Perce Wars.

Cattle ranching has long been central to Montana's history and economy. The Grant-Kohrs Ranch National Historic Site in Deer Lodge Valley is maintained as a link to the ranching style of the late 19th century. It is operated by the National Park Service but is also a 1,900-acre (7.7 km²) working ranch.

The state was the first to elect a female member of Congress (Jeannette Rankin), and was one of the first states to give women voting rights (see suffrage). Despite its sizable American Indian population, Montana is one of the most homogenous states — nearly 90% of its residents are of European descent, with a large number of immigrants of German, Irish, Norwegian, Welsh, Cornish, Italian, Slovak and Scandinavian heritage arriving in the late 19th and early 20th centuries. A significant portion of Chinese (Cantonese) immigrants also came and left an indelible mark on the state, especially in the mining cities of Helena, Butte, and Anaconda.

Historically, Montana was a Swing state of cross-ticket voters with a tradition of sending "conservatives to Helena (the state capital) and liberals to Washington." However, there have also been long-term shifts of party control. During the 1970s, the state was dominated by the Democratic Party, with Democratic governors for a 20-year period, and a Democratic majority of both the national congressional delegation and during many sessions of the state legislature. This pattern shifted, beginning with the 1988 election, when Montana elected a Republican governor and sent a Republican to the U.S. Senate for the first time since the 1940s. This shift continued with the reapportionment of the state's legislative districts that took effect in 1994, when the Republican Party took control of both houses of the state legislature, consolidating a party dominance that lasted until 2004. The state last supported a Democrat for president in 1992, Bill Clinton's first election.

Thus, in recent years, Montana has been classified as a Republican-leaning state, and the state supported President George W. Bush by a wide margin in 2000 and 2004. However, since the 2000 reapportionment plan went into effect in 2004, Democrats have fared better. The state currently has a Democratic governor (Brian Schweitzer) elected in 2004, and a Democrat-controlled state legislature. In the 2006 midterm elections, Democratic candidate Jon Tester defeated incumbent Republican Senator Conrad Burns, one of several crucial races that allowed the Democratic Party to win the majority in the Senate.

The economy is primarily based on agriculture--wheat, barley, sugar beets, oats, rye, seed potatoes, honey, cherries, cattle and sheep ranching--and significant lumber and mineral extraction (gold, coal, silver, talc, and vermiculite). Tourism is also important to the economy with millions of visitors a year to Glacier National Park, Flathead Lake, the Missouri River headwaters, the site of the Battle of Little Bighorn and three of the five entrances to Yellowstone National Park.

Montana personal income tax contains 7 brackets, with rates ranging from 1% to 6.9%. Montana has no sales tax. In Montana, household goods are exempt from property taxes. However, property taxes are assessed on livestock, farm machinery, heavy equipment, automobiles, trucks and business equipment. The amount of property tax owed is not determined solely by the property's value. The property's value is multiplied by a tax rate, set by the Montana Legislature, to determine its taxable value. The taxable value is then multiplied by the mill levy established by various taxing jurisdictions -- city and county government, school districts and others.