These data were compiled from pitfall traps deployed at three sites, along a 25 kilometers (km) stretch of the Colorado River, immediately downstream of Glen Canyon Dam, in Glen Canyon National Recreation Area. Each site had both pre and post-dam riparian habitats present. The purpose of the sampling was to determine if arthropod abundance, diversity and feeding guilds differed between habitats. Sampling for ground-dwelling arthropods using pitfall traps occurred continuously between June 17 and September 9, 2009. The site numbering proceeds from Glen Canyon Dam to Lees Ferry. Transects were composed of 10 pitfall traps approximately 10 meters apart in a line parallel with the river in both zones (Upper riparian zone (pre-dam habitat) and Lower riparian zone (post-dam habitat). Sample processing of three target groups occurred in labs at Northern Arizona University (Coleoptera and Hymenoptera, mostly ants) and University of New Mexico (Class Arachnida, mostly spiders). Species were classified into one of four feeding guilds (omnivores, detritivores, predators, and herbivores) based on published characteristics reported at the level of genus or family.