The following important events in the history of Montana affected political boundaries, record keeping, and family movements.

1803-1850s	The United States acquired from France the area of Montana east of the mountains. Britain relinquished its claims to the western section in 1846. Until the 1850s, Montana was the domain of Indians, explorers, fur traders, trappers, and missionaries.
1841	Jesuit priests founded St. Mary's mission. In the 1850s this mission became the center of ranching activity in the Bitterroot Valley of western Montana.
1846	Fort Benton, the only Montana trading post to become a permanent settlement, was established on the Missouri River.
1859	Steamboats first reached Fort Benton.
1860s	Montana west of the continental divide was designated Missoula County, Washington Territory, in 1860. In 1861 the unsettled eastern portion was attached to Dakota Territory. In 1863 and 1864 all of Montana was included in Idaho Territory.
1862-1864	The discovery of gold in western Montana brought an influx of miners to Bannack, Virginia City, and Helena. Many of the miners began farming and set up supply centers—such as Missoula, Deer Lodge, and Bozeman.
1864	Montana Territory was established with nine counties.
1880s	Railroads first crossed Montana. The population of the territory was about 40,000.
1889	Montana became a state.
1910-1925	The number of counties doubled from 28 to the present 56 as homesteaders moved into eastern Montana. By 1930 a cycle of drought years had driven many of the settlers from the state.