The National Park Service is currently involved in efforts to monitor vital signs of park condition.  Aquatic macroinvertebrate biotic integrity ranks high as one potential vital sign of interest to park staff and partnering agencies. However, many parks lack baseline data from which monitoring programs might be based.  The objective of this effort was to characterize macroinvertebrate communities inhabiting lotic habitats within parks of the Northern Great Plains Network, USA.  Invertebrate sweepnet samples (500 um) were collected from 51 headwater, middle and lower reaches during the summers of 2004 and 2005.  The total number of unique invertebrate taxa was greater from middle (219) than headwater (8) or lower (179) reaches.  Average invertebrate abundance was also slightly greater from middle (545) than lower (449) reaches but much greater than that observed from headwater (32) reaches.  Although collector-gatherers were abundant from all sites, feeding and habit guilds did generally shift according to RCC predictions.  Hilsenhoff Biotic Index values ranged widely (0.90-9.00) but average values were similar among headwater, middle and lower stream reaches.  Over 70% of the variability among sites was explained by two principle components.  Site cluster locations in ordination space were highly correlated with tolerance to organic pollution and diversity.