Mima Mounds Natural Area Preserve

Mima Mounds Natural Area Preserve is a state-protected Natural Area in the southwest corner of Thurston County, Washington, on the outwash plain of the Vashon Glacier.^[2] It was established in 1966 to protect examples of mima mounds.

Mima Mounds Natural Area Preserve
IUCN category III (natural monument or feature)
Mima Mounds in May of 2023
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Location	Southwest corner of Thurston County, Washington, United States
Nearest town	Littlerock, Washington
Coordinates	46.89°N 123.05°W / 46.89; -123.05
Area	756 acres (306 ha)
Established	1976[1]
Governing body	Washington Department of Natural Resources
Website	www.dnr.wa.gov/MimaMounds

History

Mima area in June 1941

The mounds were formed approximately 15,000 years due to glacial retreat. Indigenous people used controlled burns at the site to maintain the landscape as a prairie, allowing vegetation used for food or medicine to prosper.^[3] The mounds were documented by Charles Wilkes on May 20, 1841, who speculated they were burial sites.^[4][2]

In 1966, the mounds were designated a National Natural Landmark. The origins of the word, mima (MY-ma), is unknown.^[3]

Geography

The mounds were once part of a larger stretch of a prairie ecosystem encompassing approximately 180,000 acres (73,000 ha), spanning from present-day Joint Base Lewis–McChord through Chehalis and into Oakville. The preserve is located between Capitol State Forest and the community of Littlerock.^[3]

Features

There are approximately 8-10 mounds per acre, measuring 1–7 feet (0.30–2.13 m) in height and having a diameter of 8–40 feet (2.4–12.2 m).^[5][6]

Ecology and environment

The landscape contains natural vegetation such as Camas lilies, huckleberry, Indian plum, and salal. The mounds are usually covered in various shades of lichen and moss. Gophers are native to the area since the glaciers retreated.^[3] The site contains 756 acres (306 ha) of Garry oak woodland, oak savanna, and prairie grasslands.^[1][7]

Golden paintbrush, once common on the prairie and at the preserve, is considered a threatened species. Invasive plants include Douglas fir and Scotch broom.^[3]

Butterflies

The preserve is host to wildflowers and many species of butterfly (some endangered), with activity between spring and early fall, mid-morning and mid-afternoon.^[8]

• Common wood-nymph
• Coenonympha tullia
• Vanessa cardui (rare; migratory)
• Vanessa atalanta
• Lorquin's admiral
• Boloria epithore (late April-May)
• Speyeria zerene
• Euphydryas editha taylori (endangered^[9])
• Polites mardon (endangered^[10])
• Polites sonora (late May-August)
• Ochlodes sylvanoides
• Papilio zelicaon (May, July-August)
• Papilio eurymedon (April-October)
• Papilio rutulus
• Anthocharis sara
• Callophrys augustinus
• Callophrys polios
• Icaricia icarioides blackmorei
• Glaucopsyche lygdamus (March-June)
• Great spangled fritillary (early June-August)
• Holly blue
• Parnassius clodius
• Monarch butterfly (rare; not native to region)

Recreation

A short, ADA-accessible 0.5 mile paved trail leads to a small interpretive shelter and observation deck with view of the prairie.^[6] A longer, unpaved gravel 1.5 mile loop trail to the south explores the mounds with possible views of Mount Rainier and Mount St. Helens.^[11][12]

Gallery

• 
  NPS plaque designating the landmark.
• 
  Trees and mounds in May 2023.
• 
  Picnic area with view of mounds in March 2021.
• 
  Observation structure with information graphics.

See also

• Mima mounds
• Mima, Washington
• Rocky Prairie
• Capitol State Forest