The advantages of maize cobs as cellulosic feedstock are based on their compact architecture and high fraction of cellulose and hemicellulose. Cobs are low in ash content, nutrients, and minerals and their harvest will likely not deplete the soil. Dual-purpose maize, with larger cob biomass and high tissue density, could reduce transport costs providing more farmers with additional income from cob sales. The objective of this study was to lay the foundation for developing dual-purpose maize, combining high cob biomass and grain yield. This included a morphological and genetic analysis of cob characters under varying environments, as well as their relationships to grain yield. In addition, as starting point for further research of cob biomass traits, novel germplasm was developed including a biparental doubled haploid population. Overall, grain yield was positively correlated with all cob architecture traits but independent from cob density. Gene mapping experiments were performed in two different two intermated B73 x Mo17 (IBM) populations under varying nitrogen managements. For cob tissue density, two of the largest QTL were identified in both IBM populations on chromosomes 5 and 7 each explaining 7.7-10.7% of the phenotypic variation. These regions are known to contain candidate genes ra1 and ba2, involved in branching and branch elongation. Available maize accessions with extreme cob architecture likely carry novel alleles or genes for cob size and tissue density. Using this potential from new resources in combination with the findings and summarized information for cob biomass genetics from this research further progress with developing dual purpose maize varieties can be accomplished.