Mima Mounds Natural Area Preserve
Waddell Creek Rd SW
Littlerock, WA
Thousands of grassy mounds nobody can fully explain, spread across one of the last remnants of native Puget prairie.
Mima Mounds Natural Area Preserve protects a prairie covered in thousands of low, rounded earthen mounds, each one from about two to seven feet tall and up to forty feet across, rolling away in every direction like a frozen sea. A short paved loop, a viewing platform, and grass trails let you walk right out among them.
The mounds are famous because no one has ever proven how they formed. They are generally thought to have taken shape within the last sixteen thousand years, after the Ice Age glaciers pulled back, but beyond that there are more than thirty documented theories and still no consensus. It is one of the Northwest's great open scientific questions, sitting in plain sight.
What Guests Love
- Walking a boardwalk and easy loops through a field of mounds that has stumped scientists for over a century
- Climbing the small viewing platform to see the strange, rippled pattern spread across the whole prairie
- A rare surviving patch of native Puget prairie, ablaze with wildflowers in spring
- A quick, flat, family-friendly stop with real scientific intrigue
Worth Knowing
- There is no single accepted explanation for the mounds, which is the whole point, so come for the mystery, not an answer
- Spring, roughly April into June, is by far the best time for the wildflower bloom on the prairie
- It is open, exposed grassland with little shade, so bring sun protection on warm days
- A Washington Discover Pass is required to park
Details
Littlerock, WA
Learn about Mima Mounds Natural Area Preserve
The mystery of the mounds
People have argued about the Mima Mounds for well over a century, and the theories are wonderfully varied. The one with the most staying power came in 1942, when a University of Washington student and a federal biologist proposed in a geology journal that generations of pocket gophers, pushing soil toward their burrows, slowly built the mounds up over time.
Others have looked to bigger forces. Some geologists argue the mounds were left by a glacial outburst flood in the Puget lowland during the last Ice Age. In 1990 a geologist suggested that the shaking of earthquakes could pile loose soil into regular mounds. Still other ideas involve sediment dropped into melting ice pits, or the way water-soaked ground heaves as it freezes and thaws. As of today, no explanation has won out, and that unresolved argument is much of what makes the place worth seeing.
A last piece of Puget prairie
Long before the mounds were a curiosity, this was prairie, and prairie is now one of the rarest habitats in western Washington. Most of the Puget lowland's open grasslands were plowed, paved, or grown over with forest once the fires that once maintained them stopped. Mima Mounds, protected as a preserve in 1976, is one of the finest surviving remnants.
For thousands of years these prairies were not simply wild. Coast Salish peoples of the south Puget Sound tended them with regular burning that kept the forest back and encouraged camas, the blue-flowered lily whose bulb was a staple food. The open, mound-dotted grassland you walk through is in part a landscape that Native people shaped and kept.
The bloom and the grassland life
In spring the prairie comes alive. Camas turns whole swaths of the ground blue, and it mixes with buttercup, western blue-eyed grass, shooting star, and later the drifts of native flowers that make an April or May visit unforgettable. This is also prime habitat for rare prairie species, including butterflies and birds that depend on the vanishing grassland.
Look for hawks hunting over the open ground, listen for meadowlarks, and watch for the pocket gophers whose diggings, fittingly, are still part of the story. In summer the prairie dries to gold, and in the quiet months it is a peaceful place to walk and puzzle over the ground beneath your feet.
Closest Boutels
The closest Boutel™ stays, so you can turn this stop into an overnight. Each is an independently owned, editorially selected place to stay.
Things to Do Near Littlerock
Wolf Haven International
About 5 miles south
A sanctuary near Tenino that cares for rescued and captive-born wolves, offering guided walks past the enclosures and a look at wolf recovery in the West.
Capitol State Forest
Adjacent to the preserve
A large working forest with miles of trails for hiking, mountain biking, and horseback riding across the hills west of the mounds.
Olympia and the Washington State Capitol
About 15 miles north
The state capital, with its landmark domed Legislative Building, waterfront, farmers market, and the tidal flats of Budd Inlet.