This research assessed the geospatial supply of cellulosic feedstocks for potential mill sites in Kansas (KS), with procurement zones extending to Arkansas (AR), Iowa (IA), Missouri (MO), Oklahoma (OK), and Nebraska (NE). A web-based modeling system, the Kansas Biomass Supply Assessment Tool, was developed to identify least-cost sourcing areas for logging residues and upland hardwood roundwood biomass feedstocks. Geospatial boundaries were used according to the 5-digit zip code tabulation area (ZCTA). This higher level of resolution advanced the understanding of the geospatial economics of modeling the supply chain for cellulosic feedstocks. The analyses were conducted for six sub-regions (Chanute, Effingham, El Dorado, Manhattan, Ottawa, and Pratt) within Kansas that were identified by the US Forest Service as suitable for forest habitat. Atchison County of Effingham region had the least marginal costs for upland hardwood roundwood, ranging from $92.59 to $108.68 per dry metric ton, with an available annual supply of approximately 72 thousand dry metric tons. The least favorable was the El Dorado region, where the marginal costs ranged from $97.32 to $108.05 per dry metric ton, with an annual supply of approximately 4.4 thousand dry metric tons.