Hartley Fort State PreserveHartley Fort State Preserve is a state preserve located on the Upper [Iowa River] in the Driftless Area, in Allamakee County, Iowa, United States.GeographyHartley Fort State Preserve sits on a terrace about above the Upper Iowa, upstream of the confluence with the Upper Mississippi River.Native AmericansThe site is noted for remains of a fortified Native American effigy mound settlement. The mound builder people's era ruins seem to be associated with the Woodland period Oneota and Cahokia cultures.AccessThe Iowa Hartley Fort State Preserve land is privately owned, and there is currently no public access.