2017 Map of Twentyone Divide

About this map

Twentyone Divide serves as a prominent topographic spine along the border of Wyoming and South Dakota, where the High Plains meet the edges of the Black Hills. This high ground separates drainage basins feeding into Lone Tree Cr to the north and the meandering Cheyenne River to the south. The landscape is dominated by large-scale public land management, with significant portions of the eastern half dedicated to the Buffalo Gap National Grassland and a corner of the Black Hills National Forest. The map documents a sparse network of county infrastructure, including Argentine Rd and several rural routes like Co Hwy 9, which navigate the complex drainages of Pass Cr and Beaver Cr. The terrain is defined by the deep incisions of Twentyone Draw, illustrating the erosion patterns characteristic of this semi-arid ranching and grazing frontier.