The Flint Hills is a group of hills, mostly located in eastern Kansas. They are believed to have been formed by the erosion of limestone and shale during the Permian Period about 250 million years ago. The land is not particularly suited for farming, so tallgrass prairie makes up much of the Flint Hills. Many people want to preserve this, as it is one of the last remaining such areas in the United States, and this has led to controversy as some developers want to build wind turbines in the Flint Hills. An example of an environmental activist group opposing this is Protect the Flint Hills. The idea of the Flint Hills being a target for environmental protection is not new - legislation was passed in 1996 creating the Tallgrass Prairie National Reserve near Cottonwood Falls, Kansas.
The Flint Hills are very biologically diverse. Kansas has hundreds of species of wildflowers and birds, many of which can be found in the Flint Hills. Dozens of butterfly species can also be found there, along with a myriad of other types of animals, and over 400 plant species. Although bison are not as abundant as they used to be, they can still be observed in this area at the Maxwell Refuge, about 60 miles north of Wichita.