With 510 acres, Big Sand Mound is home to undisturbed prairies, shallow ponds and woodlands, and it has the highest concentration of threatened and endangered species in the state. Of more than 400 different plants at the site, 80 percent are native. The preserve is jointly owned by MidAmerican Energy Company and Monsanto Company, with MidAmerican Energy owning 420 acres and Monsanto owning 90. The sand prairie of Big Sand Mound Nature Preserve in unlike any other sand prairie in Iowa, the result of sentiment residue from glacier melt.