Overland pioneer route to the northwestern United States. About 3200 km, about 2000 mi long, the trail extended from Independence, Missouri, to the Columbia River in Oregon. Part of the route followed the Platte River for 870 km (540 mi) through what is now Nebraska to Fort Laramie in present-day Wyoming. The trail continued along the North Platte and Sweetwater rivers to South Pass in the Wind River Range of the Rocky Mountains.

From there the main trail went south to Fort Bridger, Wyoming, before turning into the Bear River valley and north to Fort Hall in present-day Idaho. In Idaho the Oregon Trail followed the Snake River to the Salmon Falls and then went north past Fort Boise (now Boise). The route entered what is now Oregon, passed through the Grande Ronde River valley, crossed the Blue Mountains and followed the Umatilla River to the Columbia River. Shorter and more direct routes were developed a longsome parts of the trail, but they were often more difficult. Originally, like many other main routes in the United States, sections of the Oregon Trail had been used by the Native Americans and trappers.

As early as 1742, part of the trail in Wyoming had been blazed by the Canadian explorer Pierre Gaultier de Varennes, si eur de La V'; the Lewis and Clark Expedition, between 1804 and 1806, made more of it known. The German-American fur trader and financier John Jacob Astor, in establishing his trading posts, dispatched a party overland in 1811 to follow the trail of these explorers. Later, mountain men such as James Bridger, who founded Fort Bridger in 1843, contributed their knowledge of the trail and often acted as guides. The first emigrant wagon train, headed by the American pioneer physician Elijah White, reached Oregon in 1842. The trip took the early pioneers four to six months, a journey fraught with much hardship resulting from poor equipment, illness, and attack by the Native Americans, for whom the growing number of pioneers on the trail was a never-constant threat. At first, the termination point of the Oregon Trail was Oregon City, Oregon; later, settlers continued south to the fertile and valuable land in the Willamette Valley..