Effigy Mounds National Monument preserves three prehistoric sites in Allamakee County and Clayton County, Iowa in the midwestern United States. The North Unit (67 mounds) and South Unit (29 mounds) are located where the counties meet along the Mississippi River. They are contiguous and easily accessible. The Sny Magill Unit (112 mounds) is approximately 11 miles (17 km) south of the other units, and offers no visitor facilities. It forms the heart of a cluster of interrelated protected areas. It is adjacent to the Upper Mississippi River National Wildlife and Fish Refuge, the Driftless Area National Wildlife Refuge, the Yellow River State Forest, and a short distance to the south, Pikes Peak State Park. There are also a number of state-owned wildlife management areas, such as the one at Sny Magill Creek, where Clayton County also maintains a county park.
patchy remnants of Pre-Illinoian glacial drift more than 500,000 years old recently have been discovered in the area. Unlike the rest of Iowa, the Paleozoic Plateau was bypassed by the last of the Pleistocene glaciers (the Wisconsin), allowing the region's fast cutting streams to expose and carve out deep channels in the bedrock-dominated terrain. The area is characterized by thin loess soil cover, isolated patches of glacial drift, deeply entrenched river valleys, and karst (sinkholes, caves, and springs) topography.The adjacent National Wildlife Refuge takes its name from this region.
Prehistoric mounds are common from the plains of the Midwest to the Atlantic seaboard, but only in this general area was there a culture that regularly constructed mounds in the shape of mammals, birds, or reptiles. The monument contains 2,526 acres (10 km²) with 206 mounds of which 31 are effigies. The others are conical, linear and compound. Woodland period Indians built mounds from about 500 BC until the early European contact period. When the American prairies were plowed under by European settlers for agriculture, many mound sites were lost. Effigy Mounds National Monument is the largest known collection of mounds in the United States.
Examining the geography of the region reveals why human cultures have occupied this part of the country for so long. Historically, most of the Great Plains to the west of the Mississippi River was covered in grasslands, which are very prone to fires that keep trees from becoming established. Here in extreme northeastern Iowa, the Effigy Mounds area was a point of transition between the eastern hardwood forests and the central prairies. Native American and early settlers would have been able to draw on natural resources available in forests, wetlands, and prairies, making the site hospitable for humans for many centuries.
The visitor center, located at the park entrance, contains museum exhibits highlighting archaeological and natural specimens, an auditorium and book sales outlet. The park has eleven miles of hiking trails. No roads exist in the park. Rangers give guided hikes and prehistoric tool demonstrations, mid June through Labor Day weekend. Educational programs are presented on- and off-site by appointment.
Natural features in the monument include forests, tallgrass prairies, wetlands and rivers. There are no lodging or camping facilities in the park. Excellent camping is available at nearby Pikes Peak State Park and Yellow River State Forest in Iowa; there is also Wyalusing State Park in Wisconsin. Various primitive campgrounds exist in the area as well. The national monument is quite close to the town of Marquette, Iowa, and is just across the Mississippi River from the city of Prairie du Chien, Wisconsin, where ample motel and gambling-boat facilities exist.
It was proclaimed a National Monument on October 25, 1949. As a historic unit under the National Park Service, the National Monument was administratively listed on the National Register of Historic Places on October 15, 1966.