The monument is in a transition zone of several vegetation communities. The microclimates produced from the north-facing slopes and the influence of the river valley provide habitat for a mixture of plants found nowhere else in Iowa. The prehistoric vegetation on the monument’s uplands was a forest dominated by sugar maple and basswood, with scattered prairie openings on the ridgetops and bluff edges. Current vegetation types are probably similar to those of the mound-building period, with the majority of the uplands and bluffs being forested. However, exotic grasses and pockets of prairie species now dominate openings, and pioneer species of shrubs, saplings, and small trees are gradually encroaching into the openings. The monument was created from the acquisition of private land that had been farmed and logged altering the native vegetation mosaic. Results of monument vegetation surveys combined with information from federal land surveys show that a mosaic of forest, savanna, and prairie covered the monument. Prairie and savanna dominated ridges and south facing slopes. Forests dominated the north facing slopes and the river floodplains.