Prairie cordgrass (Spartina pectinataLink.) is indigenous throughout most of the continental United States and Canada to 60°N latitude and is well suited to marginal land too wet for maize (Zea maysL.) and switchgrass (Panicum virgatumL.). Evaluations of prairie cordgrass in Europe and North America indicated it has high potential for biomass production, relative to switchgrass, in short-season areas. Our objective was to describe morphology and biomass production and partitioning in mature stands of ‘Red River’ prairie cordgrass and determine biomass production of natural populations on marginal land. This study was conducted from 2000 to 2008 in eastern South Dakota. Mean biomass production of mature stands of Red River was 12.7 Mg ha−1. Leaves composed >88% of the biomass, and 60% of the tillers had no internodes. Belowground biomass to a depth of approximately 25 cm, not including roots, was 21 Mg ha−1. Tiller density ranged from 683 tillers m−2 for a 10-year-old stand to 1140 tillers m−2 for a 4-year-old stand. The proaxis was composed of about eight phytomers, with rhizomes originating at proximal nodes and erect tillers at distal nodes. Vegetative propagation was achieved by both phalanx and guerilla growth. Differences among natural populations for biomass were expressed on gravelly marginal land. However, production, averaged across populations, was low (1.37 Mg ha−1) and comparable to ‘Cave-In-Rock’ switchgrass (1.67 Mg ha−1) over a 4-year period. The large carbon storage capacity of prairie cordgrass in proaxes and rhizomes makes it useful for carbon sequestration purposes. Prairie cordgrass should be compared with switchgrass and other C4 perennial grasses along environmental gradients to determine optimum landscape positions for each and to maximize bioenergy production and minimize inputs.