Fort Johnson was a U.S. Army post built on bluffs overlooking the Mississippi River in modern-day Warsaw, Illinois during the War of 1812. The fort was established in September 1814 by Major Zachary Taylor, future U.S. president. Troops retreating from the Battle of Credit Island constructed the fort after effectively surrendering control of the upper Mississippi to the British and allied Indian tribes, including the Sauk. The fort, which held a full company of men, was completed in just a few weeks, and had a commanding view of the Mississippi valley, the mouth of the Des Moines River, and the foot of the Des Moines Rapids. Because of the chaotic situation along the Mississippi River frontier, the fort was abandoned in late October 1814 after provisions ran out. The company retreated to Cap au Gris near St. Louis.