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 with 195 mounds of which 31 are effigies. The others are conical, linear and compound. Eastern Woodland Indians built mounds from about 500 BC until the early European contact period. Natural features in the monument include forests, tallgrass prairies, wetlands and rivers. 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, June 11 through Labor Day weekend. Educational programs are presented on- and off-site by appointment. There are no lodging or camping facilities in the park. Nearest camping is at Pikes Peak State Park and Yellow River State Forest in Iowa and Wyalusing State Park in Wisconsin. Various primitive campgrounds exist in the area as well.

In 1804, Meriwether Lewis & William Clark began a voyage of discovery with 45 men, a keelboat, two pirogues,and a dog. They departed from Camp Wood located in what was to become Illinois. They traveled over a three-year period through lands that later became 11 states. Most of the trail follows the Missouri & Columbia Rivers. Much has changed in 200 years but trail portions remain intact. At 3700 miles, Lewis & Clark NHT is the second longest of the 23 National Scenic & National Historic Trails. It begins at Hartford, IL & passes through portions of MO, KS, IA, NE, SD, ND, MT, ID, OR, & WA. Many people follow the trail by auto; others find adventure in the sections that encourage boating, biking, or hiking. You can still see the White Cliffs in Montana as Lewis & Clark did. You may stand where they stood looking over the rolling plains at Spirit Mound in South Dakota. You might meet the descendants of the people who hosted Lewis & Clark all along the trail. It remains for your discovery.