- 11,000 B.C. Earliest evidence of humans in Montana.
- A.D. 1620s Arrival of the Plains Indians.
- 1803 The eastern part of Montana becomes a territory through the Louisiana Purchase.
- 1805-06 Explorers Lewis and Clark journey through the northern Rockies to and from the Pacific coast.
- 1864 Montana becomes an official territory. Gold is discovered at Last Chance Gulch in Helena.
- 1876 Defeat of George A. Custer at the Battle of the Little Bighorn.
- 1877 Chief Joseph of the Nez Perce tribe surrenders to U.S. soldiers in the Bear Paw Mountains.
- 1880 The Utah and Northern Railroad enters Montana.
- 1883 The Northern Pacific Railroad crosses Montana.
- 1889 Montana, on November 8, becomes the 41st state in the Union.
- 1893 The University of Montana in Missoula and Montana State University in Bozeman are founded.
- 1910 Glacier National Park is established.
- 1917-19 Missoula native Jeannette Rankin, a Republican, becomes the first woman elected to U.S. Congress and votes against U.S. participation in World War I.
- 1940 Fort Peck Dam is completed.
- 1965 Construction of Yellowtail Dam is completed.
- 1973 Montana's third state constitution goes into effect.
- 1983 Anaconda Copper Mining Company shuts down.
- 1986 Montana spends $56 million on environmental protection programs.
- 1995 Wolves are reintroduced into Yellowstone National Park. Daytime speed limits are abolished (but later reestablished).
- 1996 Recluse Theodore Kaczynski, dubbed the Unabomber, is arrested at his cabin near Lincoln and is later sentenced to life in prison for sending a series of mail bombs that killed three people.
- 1998 The $6-million Lewis & Clark National Historic Trail Interpretive Center opens in Great Falls.
- 2000-01 A series of forest fires -- mostly wildfires but some caused by careless humans -- drive thousands of people from their homes and do millions of dollars in damage.
- 2003 Wildfires burn 140,000 acres in Glacier National Park.
- 2005 The grizzly bear is removed from the endangered-species list.
- 2006 A powerful November rainstorm washes out a chunk of Going-to-the-Sun Road in Glacier National Park.
- 2007-08 Over 1500 Yellowstone bison are killed as they cross into Montana due to brucellosis fears.