Tallgrass Prairie National Preserve is a United States National Preserve located in the Flint Hills region of Kansas, north of Strong City. The preserve protects a nationally significant example of the once vast tallgrass prairie ecosystem. Of the 400,000 square miles (1,000,000 km2) of tallgrass prairie that once covered the North American continent, less than 4% remains, primarily in the Flint Hills. Since 2009, the preserve has been home to the growing Tallgrass Prairie bison herd.