Hartley Fort State Preserve is a 2-acre (8,100 m2) state preserve located on the Upper Iowa River in the Driftless Area, in Allamakee County, Iowa, United States.
Hartley Fort State Preserve sits on a terrace about 80 feet (24 m) above the Upper Iowa, seven miles (11 km) upstream of the confluence with the Upper Mississippi River.
The 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.
The Iowa Hartley Fort State Preserve land is privately owned, and there is currently no public access.