Fort Jefferson was a small stockade built by Virginia in 1780 at the mouth of the Ohio in present-day Kentucky during the American Revolutionary War. Constructed by Clark’s Illinois Battalion at a strategic river junction, it was intended to protect trade and military supplies moving between Virginia and Spanish Louisiana and to support frontier defense. Although Thomas Jefferson approved the project in January 1780 on the condition that the land be purchased from the Chickasaw and that construction await their consent, that requirement was ignored. The Chickasaw saw the site as their hunting grounds, and the unauthorized occupation helped doom the fort, which was abandoned in June 1781.