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.

• Earthwork (archaeology)

• Iowa Preserves Guide - see Hartley Fort State Preserve, pg. 69
• Minutes of State Preserves Advisory Board, June 13, 1994
• Federal Register, March 25, 2004 (Volume 69, Number 58) Retrieved July 16, 2007
• Theler, James L. and Boszhardt, Robert F. "The end of the effigy mound culture: The late woodland to Oneota transition in southwestern Wisconsin", Midcontinental Journal of Archaeology, Fall 2000, Retrieved July 16, 2007
• http://sargasso.gis.iastate.edu/preserves/preserve.asp?Preserve=34^{[permanent dead link]} - Iowa Department of Natural Resources - Retrieved July 16, 2007 - ^{[dead link]}