High yielding native warm-season grasses could be used as renewable bioenergy feedstocks. The objective of this study was to compare biomass production potential of switchgrass (Panicum virgatum L.), big bluestem (Andropogon geradii Vitman), and indiangrass (Sorghastrum nutans L.) monocultures to all 2- and 3-way mixtures of these grasses across an east-west environmental gradient. Switchgrass, indiangrass, and big bluestem were planted as monocultures and in 2- and 3-way mixtures at four locations in western Minnesota and eastern South Dakota during May 2002. Biomass was harvested once annually after a killing frost in 2003 and 2004. Switchgrass was the dominant species in all mixtures in which its was present during establishment and the first year after establishment. However, by the second year after establishment, big bluestem was the dominant species in all mixtures in which its was present. In 2003, switchgrass monocultures produced the highest biomass followed by mixtures containing switchgrass. Indiangrass, alone or in mixtures, tended to produce the lowest biomass in 2004. In the second year after establishment, the highest biomass yields for three locations ranged from 5.0 to 9.7 Mg/ha. Cellulose, hemicellulose, lignin, and ash concentrations in biomass varied by year and location. Cellulose concentration tended to be higher in indiangrass while hemicellulose concentration tended to be higher in switchgrass. These results indicate that switchgrass, big bluestem, and indiangrass monocultures and mixtures containing these three species have potential as biomass feedstocks in the northern Great Plains.