

| 1743 | Discovery of the Rocky Mountains somewhere in the vicinity of Yellowstone Park made by Pierre De la Verendrye, while in search of a western sea. |
NORTHWEST TERRITORY 1803-1847
| 1803 | The Louisiana Territory, which extended west of the Mississippi to Idaho, purchased by the United States from France for $15 million. |
| 1805 | Captains Meriwether Lewis and William Clark discover Idaho at Lemhi Pass, and cross into north Idaho over the Lolo Trail August 12. Lewis and Clark sail past Spalding October 8, meet with Nez Perce Indians at Weippe Prairie. |
| 1806 | Lewis and Clark spend more than six weeks with the Nez Perce Indians in the Kamiah area before returning eastward across the Lolo Trail. |
| 1810 | David Thompson commences fur trade near Bonners Ferry. 1809 David Thompson constructs Kullyspell House by Lake Pend Oreille. First establishment erected in the Northwest, built for the Northwest Fur Company. |
| 1810 | Missouri Fur Company establishes Fort Henry near St. Anthony, first American trading post. |
| 1811 | Pacific Fur Company expedition, the Astorians, explore the Snake River Valley on their way to the Columbia River. Led by Wilson P. Hunt, the westward journey discovers the Boise Valley. |
| 1812 | Donald Mackenzie establishes a winter fur trading post at Lewiston for the Astorians. |
| 1813 | John Reid starts fur trading post on the lower Boise River, but Bannock Indians wipe it out in 1814. |
| 1818 | Donald Mackenzie makes first exploration of southern Idaho with his Snake River expedition of trappers. Treaty of joint occupancy between Great Britain and the United States leaves Oregon country (including Idaho) open to citizens of both nations. |
| 1820 | Treaty between Spain and U.S. establishes the southern boundary of Idaho (Oregon Territory) at 42nd parallel. |
| 1823 | Battle fought in Lemhi Valley between men of the Snake River country expedition and the Piegan Indians. |
| 1824 | Alexander Ross and Jedediah Smith lead separate expeditions in exploring much of the Salmon River country. Peter Skene Ogden begins trapping in Idaho. Russia cedes Northwest Territory to United States in a treaty. |
| 1827 | Rendezvous at Bear Lake for fur trading. |
| 1829 | Rendezvous held at Pierre's Hole, now known as the Teton basin, where hundreds of mountain men and fur trappers congregated. |
| 1830 | Rendezvous with the Indians held on the Blackfoot River, where competition in fur trading became intensely keen. |
| 1831 | Fur trappers of the Rocky Mountain Fur Company, led by Kit Carson, winter on the Salmon River. |
| 1832 | Captain B.L.E. Bonneville leads the first crossing of the Rocky Mountains in covered wagons. The company reaches the Lemhi River on September 19. Rendezvous at Pierre's Hole. Battle of Pierre's Hole occurs July 18 between American fur trappers and the Grosventre Indians. |
| 1834 | Fort Hall, established by Americans under Captain Nathaniel Wyeth, becomes a hub for trails and roads to the western parts of the United States. Fort Boise erected by the Hudson Bay Company near the mouth of the Boise River. |
| 1836 | Henry Harmon Spalding establishes a Nez Perce Indian mission at Lapwai. |
| 1837 | First school in Idaho opens for Indian children at Lapwai. First white child born in Idaho is Eliza Spalding born at Lapwai. |
| 1839 | Henry Spalding starts publishing the Bible in Lapwai on the earliest printing press in the Pacific Northwest. Chief Timothy, the first native Christian leader, baptized November 17. |
| 1840 | Father Pierre Jean de Smet begins missionary work in Idaho. |
| 1842 | Father Point establishes the Jesuit Coeur d' Alene Mission of the Sacred Heart near Saint Maries. The Mission moves to a site near Cataldo in 1846, and is transferred in 1877 to Desmet where it stands today. |
| 1843 | Oregon Trail established in Idaho, which crossed the border near Montpelier, passed by Fort Hall, then westward south of the Snake River to the ford below Salmon Falls, then to Fort Boise, crossing the Snake River into Oregon. |
| 1846 | Sacred Heart Mission established on the Coeur d'Alene River. The United States acquires all land south of 49 degrees longitude by a treaty with Great Britain. |