Beginning some 2 million years ago, however, dramatic temperature changes profoundly altered what we now call Montana. At four different times, great sheets of glacial ice moved south through Canada to cover much of the north. The last glacial retreat, about 10,000 years ago, did much to carve the state's present topographic feature. Montana's first humans probably came from across the Bering Strait; their fragmentary remains indicate a presence dating between 10,000 and 4000 BC. Native Americans known to have inhabited Montana at the time Europeans first explored it included the Blackfoot, the Sioux, the Shoshone, the Arapaho, the Kootenai, the Cheyenne, the Salish, and others.
Montana is the fourth largest U.S. state by area, behind Alaska, Texas and California, but with an average of just six people per square mile, it is one of the country's least densely populated states
1680 - Montana natives acquire the horse.
1720 - Montana natives acquire the gun.
1795 - Yellowstone River named by James Mackay
1803 - United States acquires most of Montana in the Louisiana Purchase
1805-1806 - Lewis and Clark Expedition crosses and recrosses Montana
1807 - Manuel Lisa builds first fur fort in Montana on the Yellowstone River
1828 - Fort Union, an American Fur Company post, is built at the mouth of the Yellowstone River
1841 - Father Pierre Jean de Smer establishes St. Mary's Mission in the Bitterrot Valley
1846 - The Oregon Treaty gives the rest of Montana to the US
1847 - Fort Benton founded on Missouri River as military and trading post; soon becoming world-renown "Head of Navigation" to the west, and world's furthest inland port. Steamboats brought gold seekers, fur traders, settlers and supplies, making Fort Benton the "Birthplace of Montana."
1853 - Johnny Grant starts the first beef herd in the Deer Lodge Valley
1857 - First sheep ranching begins in the Bitterroot Valley
1860 - First steamboat reaches Fort Benton
1865 - Montana's first US Marshal appointed by President Lincoln: George M. Pinney, serving from 1865 to 1867. Pinney first sets up his office in Butte, later moving to Helena.
1866 - US Military Post, Camp Cooke, created on the Judith River.
1870 - Open-range cattle industry begins on Montana Prairies
1872 - Congress creates Yellowstone National Park
1873 - Beginning of Royal Canadian Mounted Police, to "destroy illegal whiskey trade and lawlessness" caused by the "Whoop-Up Trail" operation from Fort Benton into Canadian Northwest Territories, the "Trail" having been created by Fort Benton's first sheriff, and subsequently participated in and protected by five of his successors.
1880 - Utah and Northern Railroad enters Montana
1885 - Montana Territorial Government creates first "state" law enforcement agency: Montana Department of Livestock.
1889 - 08 November, Montana becomes 41st state of United States under President Benjamin Harrison's administration, 16 original counties established, and 16 sheriffs appointed by new state government.
1890 - First hydroelectric dam is built at Great Falls
1902 - Montana Capitol Building is completed.
1903 - Amalgamated Copper Company paralyzes the state's economy with the shut-down to force legislative relief.
1909 -Chicago, Milwaukee, St. Paul and Pacific Railroad ("Milwaukee Road") is completed through Montana.
1910-1918 - Homesteading boom peaks on Montana's plains.
1911-1925 - "County-busting" craze creates 25 new Montana counties.
1914 - Montana women receive the franchise (right to vote).
1916 - Jeanette Rankin elected the first woman in the US Congress.
1918 - February, Mrs Leo Hunter, Rosebud County Sheriff's Office, appointed first female law officer in state.
1919 - First of severe agricultural depressions (extending into the early 1940s) begins in Montana; oil is discovered in the Cat Creek field.
1921 - Wave of bank failures begins in Montana.
1922 - KDYS (Great Falls), Montana's first licensed radio station, broadcasts.
1923 - Jack Dempsey-Tommy Gibbons world heavyweight championship fight is staged in Shelby.
1926 - Montana artist Charlie Russell dies in Great Falls.
1930 - Significant tourist industry begins in Montana.
1936 - Rural Electrification Administration (REA) begins work in Montana
1941 - Congresswoman Jeanette Rankin votes against US entry into World War II
1943 - Smith Mine disaster kills 70 coal miners
1950 - Great Falls replaces Butte as Montana's largest city
1951 - Petroleum boom begins in eastern Montana
1952 - Mike Mansfield is first elected to the US Senate
1953 - KOOK-TV (Billings), Montana's first licensed television state, broadcasts
1956 - Construction of the federal interstate-highway system begins in Montana
1959 - Severe earthquakes hit upper Madison Valley
1961 - Malmstrom Air Force Base (Great Falls) becomes site of the nation's first ICBM missile command
1964 - Congress passes federal Wilderness Act
1968 - Yellowtail Dam is completed; Work begins on Libby Dam
1969 - Large-scale strip mining of coal begins at Colstrip
1970 - Consolidation creates the Burlington Northern Railroad
1972 - Montana's electorate approves new constitution
1975 - Underground mining ceases in Butte
1976 - Mike Mansfield retires from US Senate; becomes US ambassador to Japan
1981 - Milwaukee Road declares bankruptcy
1982 - Copper-mining operations cease at Butte's Berkeley Pit
1989 - Montana celebrates its statehood centennial
1990 - Montana's timber-industry income declines, while gains occur in tourism and specialized mining
1991 - Riot at State Prison in Deer Lodge results in five deaths.
1994 - 4,500 wildfires rage across Montana, burning 286,000 acres.
1995 - Wolves are returned to Yellowstone National Park, where they thrive.
1997 - A prison-population overflow creates a housing crisis for inmates, some sent out-of-state.
1998 - The Montana Power Company sells its electric generating facilities to Pacific Power and Light, Global, Inc.
1999 - As highway deaths rise, Montana reinstitutes a daylight speed limit of 70 mph on 2-lane paved roads.