Fort Winnebago was a 19th-century fortification of the United States Army located on a hill overlooking the eastern end of the portage between the Fox and Wisconsin Rivers east of present-day Portage, Wisconsin. It was the middle one of three fortifications along the Fox-Wisconsin Waterway that also included Fort Howard in Green Bay, Wisconsin and Fort Crawford in Prairie du Chien, Wisconsin. Fort Winnebago was constructed in 1828 as part of an effort to maintain peace between white settlers and the region's Native American tribes following the Winnebago War of 1827. The fort's location was chosen not only because of its proximity to the site of Red Bird's surrender in the Winnebago War, but also because of the strategic importance of the portage on the Fox-Wisconsin Waterway, a heavily traveled connection between the Great Lakes and the Mississippi River. Fort Winnebago's location near the portage allowed it to regulate transportation between the lakes and the Mississippi.
With the exception of the participation of troops from the fort in the 1832 Black Hawk War, Fort Winnebago was not involved in any combat operations during its occupation by the U.S. Army. Instead, the garrison, which from 1829 to 1831 included Lt. Jefferson Davis (later President of the Confederate States of America), was put to work in building a military road between Portage and Fond du Lac, Wisconsin, and assisting with the relocation of the Ho-Chunk Nation from Wisconsin to Minnesota during the 1840s. In 1845, the absence of any real threat to peace in the region prompted the abandonment of the fort. Nine years later the site was sold into private hands, and in 1856 a fire destroyed much of the fort.