Chase County (county code CS) is a county located in the U.S. state of Kansas. As of the 2010 census, the county population was 2,790. Its county seat and most populous city is Cottonwood Falls.The county has been the subject of a book, PrairyErth (A Deep Map) by William Least Heat-Moon. In 1931, Notre Dame coach Knute Rockne died in a plane crash a few miles southwest of Bazaar, in Chase County, Kansas. In 1996, the Tallgrass Prairie National Preserve was established in the county.