Chimney Rock rises above Nebraska’s North Platte River valley as one of the most famous landmarks of the overland trails. In the mid-19th century, emigrants on the Oregon, California, and Mormon trails used its distinctive shape as a key guidepost across the plains. Formed mainly of Brule clay, volcanic ash, and Arikaree sandstone, it was once taller before erosion, lightning, and possibly cannon fire reduced it. Native people, especially the Lakota Sioux, knew it long before non-Native travelers, who likely first recorded it in the early 1800s. It later became a protected historic site and an enduring symbol of westward migration.