- California Gold Rush begins, leading to a massive influx of settlers to the region.
1850
- California admitted to the Union as the 31st state.
1851-1852
- Rogue River Wars between the United States and Native Americans in southwestern Oregon.
1859
- Colorado Gold Rush begins.
- Nevada admitted to the Union as the 36th state.
1861-1865
- American Civil War
- Several battles and skirmishes take place in the West, including the Battle of Valverde in New Mexico and the Battle of Glorieta Pass in New Mexico Territory.
1862
- Homestead Act passed, allowing settlers to claim public land in the West.
- Transcontinental Telegraph completed, linking the East and West coasts.
1864
- Idaho Territory organized.
- Montana Territory organized.
1867
- Alaska Purchase: United States purchases Alaska from Russia for $7.2 million.
- Medicine Lodge Treaty signed between the United States and various Plains Indian tribes, ending the Red River War.
1869
- First transcontinental railroad completed at Promontory Summit, Utah.
1870
- Wyoming admitted to the Union as the 44th state.
1872
-Yellowstone National Park established, the first federal park in the world.
1876
- Centennial Exposition held in Philadelphia, Pennsylvania, to celebrate the 100th anniversary of the signing of the Declaration of Independence.
- Battle of the Little Bighorn: Lakota Sioux and Northern Cheyenne defeat the U.S. 7th Cavalry under the command of George Armstrong Custer.
1879
- Oregon admitted to the Union as the 33rd state.
1889
- Washington admitted to the Union as the 42nd state.
- Oklahoma Territory organized.
- Geronimo surrenders to the United States Army, effectively ending the Apache Wars.
1890
- Idaho admitted to the Union as the 43rd state.
- Wyoming becomes the first state to grant women the right to vote.
1896
- Utah admitted to the Union as the 45th state.
1900
- California Gold Rush ends.