Fort Atkinson was founded in 1840 as a temporary post to keep the Winnebago (Ho-Chunk) Indians west of the Mississippi River on the Neutral Ground after their removal from Wisconsin. The Neutral Ground was intended for the exclusive use of Indians and as a buffer zone between the Sioux to the north and the Sauk and Meskwaki Indians to the south. When the Winnebago were moved into the area, troops at Fort Atkinson were responsible for maintaining peace among tribes that were sometimes hostile to one another, and patrols routinely went out from the fort to prevent Euro-American traders and settlers from illegally entering the region. The post also reinforced the authority of the Indian Sub-agent, a U.S. government official who operated a school and model farm and provided supplies for the Winnebago at the Turkey River Sub-agency about four miles downstream. Fort Atkinson followed a typical U.S. Army frontier-post design, with a rectangular layout enclosed by a wooden picket-stockade, a central parade ground, four main barrack buildings, cannon houses in the northeast and southwest corners, a powder house to the southeast, and a commissary to the northwest, while fourteen additional buildings outside the stockade included stables, a granary, a bakery, laundresses' huts, and blacksmith shops, all built of limestone or hewn logs with cut-pine shingle roofs. Three of the six years that regular troops were garrisoned there were spent constructing the fort. When those troops were called to the Mexican War in 1846, Iowa volunteer militia staffed the post until the Winnebago were removed from Iowa in 1848, and the last militia left in early 1849. In 1855 the fort was sold at public auction, and the new owners had the property surveyed and platted as the town of Fort Atkinson. The State of Iowa acquired part of the military fort in 1921 and dedicated it as a State Preserve in 1968. Most of the fort's buildings were made of stone quarried from the adjacent hillside, and in 1906 Professor Samuel Calvin, while conducting geological studies of Winneshiek County, named this stone the Fort Atkinson Limestone Member of the Maquoketa Formation and designated the quarry at the southwest corner of the old fort as the geological type section. The limestone originated in a shallow tropical sea 440 million years ago, and Fort Atkinson State Preserve is managed by the Iowa Department of Natural Resources under the guidance of the State Preserves Advisory Board.