Thousands of years after glaciers receded from this region, huge rivers and lakes gave way to a broad valley of tallgrass prairies, small lakes, and the waterway now known as the Minnesota River, where Dakota people lived throughout the valley. After the Dakota sold much of the area to the U.S. government in 1851, they lived on reservation land along the river, and in 1858 a stretch of that land, including what became Birch Coulee Battlefield, was ceded to the U.S. and opened to settlers. Because no one had settled near Birch Coulee by the time of the battle, the area remained prairie grassland dotted with wetlands, and these natural features, together with the coulee, gave Dakota forces an advantage, as the deep, steep-sided streambed provided a natural hiding place for Dakota fighters. Soon after 1862, the battle site became a farm field. In 1929 Birch Coulee State Park was established, and after the Minnesota Historical Society acquired the land in 1976, archaeological investigations and survivors' written memories helped restore some features of the battlefield to how they looked in 1862.