Prehistoric humans entered what is now Montana more than 10,000 years ago. The early inhabitants hunted the area's abundant big game. When climatic conditions caused game to decrease around 6000 B.C., the Indians turned to foraging. With the return of big game herds about 500 A.D., hunting again was adopted and continued into the period of European exploration. Major tribes of Indians at that time included the Kutenai, Pend d'Oreille, Flathead, Crow, Blackfeet, and Atsina.

In 1743 French Canadian fur traders came close enough to the present state of Montana to note its “shining mountains." In 1805–06, after the territory had passed to the United States in the Louisiana Purchase, the Lewis and Clark Expedition explored the area on its journey to the Pacific coast. American fur trappers were soon operating throughout the upper Missouri River and eastern Rocky Mountains region. The British gained control of the Oregon Country, west of the Continental Divide.

The eastern Montana area was part of Missouri Territory from 1812 to 1821, after which it was part of a huge, unorganized frontier region referred to as Indian Country. A number of trading posts were built in the area, and in 1841 Father Pierre Jean De Smet, a Belgian Jesuit, founded an Indian mission in the Bitterroot Valley. Fort Benton, established in 1847, was the first permanent settlement.

The dispute with Great Britain over the Oregon Country was settled in 1846. In 1853 western Montana became part of Washington Territory, Eastern Montana was included in Nebraska Territory, 1854–61, then became part of Dakota Territory.

Important dates in Montana
1803 Eastern Montana became U.S. territory through the Louisiana Purchase.
1805-1806 Lewis and Clark explored part of Montana on their journey to and from the Pacific Coast.
1846 The Oregon treaty with the United Kingdom made northwestern Montana part of the United States.
1862 Gold was discovered on Grasshopper Creek.
1864 Congress established the Montana Territory.
1876 The Sioux and Cheyenne Indians defeated U.S. Cavalry troops at the Battle of the Little Bighorn.
1877 Chief Joseph and the Nez Perce Indians surrendered to federal troops after several battles.
1880 The Utah & Northern Railroad entered Montana.
1883 The Northern Pacific Railroad crossed Montana.
1889 Montana became the 41st state on Nov. 8.
1910 Congress established Glacier National Park.
1940 Fort Peck Dam was completed.
1951 The first oil wells in the Montana section of the Williston Basin started production.
1955 The Anaconda Aluminum Company opened a $65-million plant at Columbia Falls.
1966 Construction of Yellowtail Dam was completed.
1973 A new state constitution went into effect.
1984 The Libby Dam hydroelectric project, begun in 1967, was completed.
2000 Judy Martz became the first woman to be elected governor of Montana. She held office from 2001 to 2005.