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.
"Item #10 - Archaeological Work at Hartley Fort / Request for archaeological testing at Hartley Fort"(PDF). Minutes of State Preserves Advisory Board. Motion was made by Martha Maxon to approve the request from Fred Finney to conduct test excavations at Hartley Fort with the three stipulations recommended by Chairperson Schermer. Seconded by Jonathan Steege. Motion carried unanimously. Charles City, Iowa: North Iowa Area Community College. June 13, 1994. pp. 2, 15. Archived from the original(PDF) on 2007-09-28.{{cite magazine}}: CS1 maint: others (link)
Theler, James L.; Boszhardt, Robert F. (Fall 2000). "The End of the Effigy Mound Culture: The Late Woodland to Oneota Transition in Southwestern Wisconsin". Midcontinental Journal of Archaeology. 25 (2). The University of Iowa: 289–312. ISSN0146-1109. JSTOR20708138.