found in Little Sioux Valley.
Snake found in Little Sioux Valley. © Sofie Jaramillo A./TNC

Places We Protect

Little Sioux Valley


The Little Sioux Valley is a priority project area for The Nature Conservancy in Iowa.


In northwestern Iowa, just southwest of Iowa’s Great Lakes region, the Little Sioux River winds its way through sand and gravel deposits left behind by glaciers 11,000 years ago, eventually making its way to the Missouri River. Prairie, river and wetland systems make up this area, which once was covered by tallgrass prairie. Native prairie remnants still exist and include prairie pothole wetlands, calcareous fens on limestone soils, dry and moderately dry hill prairies and oak woodlands.

Much of the land has been unsuitable for farming—but ideal for haying and cattle grazing because of the abundant gravel. Grazing and haying have helped maintain significant prairie tracts.

In the 1940s, botanist Dr. Ada Hayden identified the area as having some of the best native prairie left in the state and much of it still exists. Several globally rare species can be found in the Little Sioux Valley, including the federally-threatened bush clover and eastern prairie fringed orchid. Prairie grasses and wildflowers abound, along with butterflies and grassland birds such as the dickcissels and yellow warbler.

Ecological threats to the area include lack of fire, inappropriate tree planting and overly intensive grazing. Harmful non-native species also need to be controlled – for cattle as well as for native plants and animals.

The Conservancy has helped protect 2,700 acres in the Little Sioux Valley, much of it in the Iowa Department of Natural Resources Waterman Prairie Project. Conservancy preserves in the area include the 110-acre Freda Haffner Preserve, southwest of Okaboji. The preserve consists of wet and dry prairies and sedge meadows. It also is one of Iowa’s largest glacial “kettleholes,” which were formed by large blocks of ice that remained after the glaciers retreated. The Freda Haffner prairie kettlehole is one of Iowa’s most popular natural areas. Another Conservancy preserve is Mori Prairie in Clay County, a biological and geological state preserve, designated as an excellent example of Iowa blacksoil prairie. The Conservancy’s long-term goal for the Little Sioux Valley is to work with partners to conserve and restore 15,000 acres in the area.