The Mima Mounds Natural Area Preserve (NAP) was established in 1976 to protect rare examples of mima mound landforms and Puget prairie grasslands. The site includes a small garry oak woodland and savannah (widely spaced oak trees with grass understory) and also supports a variety of prairie dependent butterflies, birds and douglas-fir forest. The NAP currently comprises 637 acres of grassland covered mima mounds, forest and oak woodland. In 1966, the National Park Service designated mima mounds a National Natural Landmark, for its representation of our nation’s natural landscape. The site is one of only 17 landmarks found in Washington State.