Toolesboro Mounds State Preserve is a 3-acre preserve featuring a cluster of ancient Indian mounds. It is located just north of the town of Toolesboro in Louisa County. Archaeological studies of the mounds were conducted as early as the 1840s, and again in the 1870s and 1880s. In the 1930s, the Iowa Archaeological Survey and the State Historical Society urged the state to protect the mounds. In 1963, the Mosier family deeded the two southernmost mounds to the State Historical Society. The mound group was designated as a National Historic Landmark in 1966. The site is also listed on the National Register of Historic Places. In 1971, the State Historical Society opened the Toolesboro Visitors Center. Acquisition of the northern portion, which contained five more mounds, was completed in 1976. The site was dedicated as an archaeological state preserve in 1981.

These ancient Indian mounds overlook the Mississippi River valley near the mouth of the Iowa River in the Southern Iowa Drift Plain landform region. The preserve includes a total of seven conical mounds (that average about six to eight feet tall and forty to eighty feet in diameter), the Visitors Center and Museum, and a small reconstructed prairie. The mounds comprise one of Iowa’s principal “Hopewell” cultural sites. The Hopewell culture was a prehistoric mound-building group that established villages near rivers and streams during the Middle Woodland period, about 200 b.c. to a.d. 400. They are known for their mound-building activity and art, especially stone effigy pipes depicting frogs, rabbits, birds, and other animals.