The Great Plains of Colorado occupies over two-fifths of the state, yet very little is known about the aquatic insects of this area. This paper reports on the aquatic insects found in temporary and permanent pools of Big Sandy Creek within the Sand Creek Massacre National Historic Site, on the Great Plains of Colorado. A total of 107 distinguishable taxa were collected representing six orders and 27 families of insects. The orders Coleoptera (39% or 42 taxa), Diptera (23% or 25 taxa), and Odonata (21% or 23 species) dominated this site. Most of these taxa are geographically widespread and considered common. The aquatic beetles Thermonectus intermedius Crotch, Gyrinus parcus Say, Berosus hatchi Miller, B. infuscatus LeConte and B. miles LeConte are reported from Colorado for the first time.