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Mima Mounds Loop Hike

From Oregon Hikers Field Guide

On the northern loop, Mima Mounds (bobcat)
Harvest brodiaea (Brodiaea elegans), Mima Mounds (bobcat)
Bracken on a mound, Mima Mounds (bobcat)
Hooded ladies' tresses (Spiranthes romanzoffiana), Mima Mounds (bobcat)
The loop trails at Mima Mounds Natural Area Preserve (bobcat) Courtesy: Google Maps
  • Start point: Mima Mounds TrailheadRoad.JPG
  • End point: Mima Mounds Viewpoint
  • Trail Log:
  • Hike Type: Three connected loops
  • Distance: 3.2 miles
  • High point: 245 feet
  • Elevation gain: 30 feet
  • Difficulty: Easy
  • Seasons: Year round
  • Family Friendly: Yes
  • Backpackable: No
  • Crowded: No


Hike Description

The Mima Mounds Natural Area Preserve is one of several mysterious mound areas in the United States that are associated with the last continental ice age. In the past, there has been much disagreement over how these fairly symmetrical structures were formed, and theories abound:

  • They could be deposits from sediment pits that collected debris on the surface of an ice sheet.
  • The mounds may be a result of the permafrost layer breaking up.
  • They may have been created during glacial floods when sediment collected around clumps of vegetation.
  • Contrary to the theory above, the mounds could have been formed when glacial runoff eroded the ground around root clusters of trees, leaving soil "islands."
  • The gopher theory suggests that pocket gophers coming into the area threw up glacial till from their burrows and, over decades and perhaps centuries, the mounds developed their large size; the theory is not as far-fetched as it sounds - each mound is about the size of a pocket gopher's territory; other life forms implicated in the build up of the mounds are termites and ants.
  • The earthquake theory suggests that in a strong Cascadia-type earthquake would shake loose earth into a pattern of low symmetrical mounds corresponding to the tops of seismic waves; the analogy is flour on a cookie sheet: shake the sheet, and the flour will arrange itself in patterns.

Mima mounds exist in other parts of the world as well. It's quite possible that in different areas, there were different reasons for their formation since not all Mima mounds are internally the same. In general, however, they are formed of soft earth over a hard pan layer.

Three loop trails, including a paved universal access nature trail, allow you to explore the prairie and a slice of the forest bordering it. Brochures are not always available for the interpretive trail, and pets are not permitted on any of the trails.

The interpretive trail begins under Douglas-firs with salal, trailing blackberry, hazel and sword fern in the understory. You may hear gunshots from a sportmen’s club on the western border of the natural area. Enter the prairie on the paved trail, pass a connector to the northern loop trail, and go right to an information kiosk roofed by a viewing platform that affords a vista over the mounds, all of which are about six to eight feet high.

To complete the half-mile northern loop, hike north from the shelter about 35 yards and go right to begin the loop. The path circles around through the mounds, which bloom with bluebells, ladies' tresses, and ox-eye daisy in the summer; in the spring, the meadow is dominated by camas and spring gold, a desert parsley (It is important to remember that the preserve also protects a remnant of the Puget Prairie ecosystem). Garry (white) oaks have been planted here, and the meadow is rimmed by a mixed forest. Return to the shelter to begin your exploration of the southern section of the area.

From the domed shelter, head along the 0.5 mile universal access nature trail, passing a bloom calendar (best time is the spring). Butterflies are profuse here in late spring and summer. Reach a little boardwalk that rises to a map showing the other trails of the area. Below this, proceed right on an unpaved trail that leads to the southern part of the preserve.

This trail winds into the mounds with views of distant hills. You may be able to detect the effects of annual prescribed burns. At a junction, a side trail heads straight left along an old fence line. Keep right and come to the junction for the long loop and shortcut trails. Next, keep right at the junction with the shortcut trail. Farm buildings become closer, and the trail wends around and eventually rises to the Mima Mounds Viewpoint at the top of a mound, where you'll find a bench to sit on. Fescue grasses, red and Idaho blue, seem to dominate among the blooms, which include natives, such as camas, brodiaea, and bluebells, as well as weedy summer species like ox-eye daisy, cat's-ear, and field pussytoes. A side trail leads right as you keep left. The trail circles east at the south end of the loop. You'll notice the stumps of Douglas-firs which have been cut to help reestablish the original garry oak woodland. Kinnikinnick, reindeer lichen and a dry moss form a groundcover. In summer, there are also blooming dogbane, fireweed, and some goldenrod. Pass the junction with the east end of the shortcut loop at another bench under a young Douglas-fir. Finish the loop and go right to head back to the paved interpretive trail.

To complete the interpretive loop, keep right and enter the woods. Rein orchids bloom profusely here, and the trail eventually reaches the entry signs, where you can go right to parking.


Regulations or restrictions, etc

  • $10 day-use pass or annual Discover Pass required
  • Pets not permitted on the trails
  • Restrooms, picnic area, interpretive trail, information kiosk

Trip Reports

Related Discussions / Q&A

Guidebooks that cover this hike

  • Urban Trails: Olympia by Craig Romano
  • Best Hikes With Kids: Western Washington by Susan Elderkin

More Links


Oregon Hikers Field Guide is built as a collaborative effort by its user community. While we make every effort to fact-check, information found here should be considered anecdotal. You should cross-check against other references before planning a hike. Trail routing and conditions are subject to change. Please contact us if you notice errors on this page.

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