Locations of pivotal events that took place during the Lewis and Clark journey of 1803-1806. These places were identified by Historic Research Associates as part of a project with the National Park Service Lewis and Clark National Historic Trail.

The Lewis and Clark National Historic Trail is approximately 4,900 miles long, extending from the Ohio River in Pittsburgh, Pennsylvania to the mouth of the Columbia River in Oregon, following both the outbound and inbound routes of the Lewis and Clark Expedition. The trail connects 16 states (Pennsylvania, West Virginia, Ohio, Indiana, Kentucky, Illinois, Missouri, Kansas, Nebraska, Iowa, South Dakota, North Dakota, Montana, Idaho, Washington, and Oregon) and was established by Congress in 1978 as part of the national trails system (NTS) as one of four original national historic trails. This trail commemorates the 1803-1806 expedition of Lewis and Clark and the Corps of Discovery, which explored the Louisiana Territory and beyond. This epic journey contributed to significant scientific knowledge and profound political, social, economic, cultural, and environmental changes to the lands and the peoples of the North American continent.