Plum Bayou Mounds Archeological State Park, formerly known as "Toltec Mounds Archeological State Park", also known as Knapp Mounds, Toltec Mounds or Toltec Mounds site, is an archaeological site from the Late Woodland period in Arkansas that protects an 18-mound complex with the tallest surviving prehistoric mounds in Arkansas. The site is on the banks of Mound Lake, an oxbow lake of the Arkansas River. It was occupied by its original inhabitants from the 7th to the 11th century.