Hole-in-the-Mountain is a large prairie remnant situated on a steep valley along the outer edge of the glacial escarpment known as the Prairie Coteau. Its undulating terrain is carpeted in wildflowers during summer. The preserve provides excellent habitat for rare prairie-dependent insects, including 25 species of butterflies, and nesting waterfowl, passerines and other grassland birds. The prairie valley is the headwaters of Flandreau Creek, which runs in a southwesterly direction toward the Big Sioux River. Indians called the half-mile-wide valley "Mountain Pass" or "Hole-in-the-Mountain."
Why the Conservancy Selected This Site
Hole-In-The Mountain Prairie is a remnant of what was once a 4,300-acre prairie landscape. Much of the surrounding land is in private agricultural use. When the first tract of the preserve was acquired by The Nature Conservancy in 1978, most had been altered to some extent from their pre-settlement condition. Historically, most of this area had been used to pasture sheep and cattle on the steep slopes and parts of the floodplain. Upland flats were cultivated.
What the Conservancy Has Done/Is Doing
This preserve is managed by prescribed burning and the native prairie vegetation on the steeper slopes has recovered well in recent years. Areas of old fields have been replanted to native species. Several tracts adjacent to the preserve have been purchased by the Conservancy and transferred to the Department of Natural Resources and are managed for wildlife and natural area use.