Konza Prairie, Kansas. A rainbow brings hope at sunrise, signaling the end of an early morning thundershower while waning winds from the passing storm set in motion a hillside of butterfly milkweed, one of many colorful wildflowers that reach their peak bloom in early summer in the Flint Hills of Kansas. The tallgrass prairies of the Flint Hills stretch nearly unchecked in a thin line down the eastern third of Kansas and into northern Oklahoma, the largest intact tallgrass prairie landscape left in North America.