Turkey River Mounds State Preserve is a historic site located near the unincorporated community of Millville, Iowa, United States. The 62-acre (25 ha) preserve contains thirty-eight of forty-three Native American mounds located on a narrow Paleozoic Plateau at the confluence of the Mississippi and Turkey rivers.^[3] They vary in size and shape and are 1.3 feet (0.40 m) to 6 feet (1.8 m) in height. The conical mounds range from 20 feet (6.1 m) to over 100 feet (30 m) in diameter. The linear mounds vary from 80 feet (24 m) to 175 feet (53 m) in length. There is one effigy mound in the shape of a panther that is 98 feet (30 m) long and 40 feet (12 m) wide. There are also compound mounds in the preserve. The mounds were constructed during the Woodland period (500 BCE and 900 CE). They were used for burials and ceremonial places, and are now protected by law. The preserve is also home to a variety of trees, prairie grasses and flowers.

Turkey River Mounds State Preserve
Location of Turkey River Mounds State Preserve in Iowa
Location	Clayton, Iowa, United States
Coordinates	42°43′11″N 91°02′54″W / 42.71972°N 91.04833°W / 42.71972; -91.04833
Area	62 acres (25 ha)
Elevation	761 ft (232 m)[1]
Established	1968
Governing body	Iowa Department of Natural Resources
Turkey River State Preserve Archeological District
U.S. National Register of Historic Places
U.S. Historic district
MPS	Prehistoric Mounds of the Quad-State Region of the Upper Mississippi River Valley MPS
NRHP reference No.	90000774[2]
Added to NRHP	May 30, 1990

The mounds were first surveyed in 1885, and Ellison Orr studied them in the 1930s. People from Dubuque, Iowa bought the property in 1934 and gave it to the Iowa Conservation Commission in 1940. Other archaeological surveys were undertaken in 1964 and 1973. It was dedicated as a state preserve in 1968 for its archaeological, geological, and biological qualities.^[3] The preserve was listed on the National Register of Historic Places as a historic district in 1990.^[2]