Upper Snake Field Office

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Nine Mile Knoll &
St. Anthony Sand Dunes

Designated 1987, 1985
Medicine Lodge RMP
42,343 acres; 1,825 acres

The Nine Mile Knoll ACEC is located 6 miles west and northwest of the town of St. Anthony and encompasses all of the St. Anthony sand dunes found on public land, along with 36 square miles of vegetated desert
 to the south and southwest of the dunes.

The St. Anthony Sand Dunes RNA lies completely within the ACEC boundary.  The portion of the ACEC covered with active dunes is also designated a wilderness study area (WSA) and a special recreation management area.  The dunes have also been evaluated
 for National Natural Landmark designation.


 St. Anthony Dunes evening primrose (Oenothera psammophila)
dunes tiger beetle (Cicindela arenicola)
PHOTO above: Gordon S. Whitehead @ USDA-NRCS PLANTS

The St. Anthony Sand Dunes are the largest and most spectacular dunes in natural condition on the Columbia Plateau.  Such large sand dunes so far inland are rare and geologically significant.  Dunes range from 50 to 400 feet in height and cover a total of 175 square miles.  The sand is blown in from the Snake River Lava Plain.  Rounded hills to the north, the Juniper Buttes, are extinct volcanoes.

The ACEC protects habitat for unique wildlife: the largest and most viable population of a rare tiger beetle, known from only two other locations, and the St. Anthony Dunes evening primrose, which grows only on these dunes. 

Antelope, mule deer, moose and elk migrate long distances to winter in and around the dunes.  The wintering elk population is the largest in North America.  Seasonal human-entry closures ensure the integrity of the winter habitat. 

The RNA designation acknowledges the area's unique ecology and complex vegetative cover.  Activities in the RNA are limited to ensure that there are no changes in this vegetation.