The U.S. is the world's leading consumer of primary energy. A large fraction of this energy is used in boiler installations to generate steam and hot water for heating applications. It is estimated there are total 163,000 industrial and commercial boilers in use in the United States of all sizes. This paper characterizes the commercial and industrial boilers in the 37 states of the Midwest, Northeast, and Southern regions of the U.S. in term of number of units, unit capacity, aggregate capacity, and fuel type. A methodology is developed for evaluating and ranking the potential for converting from existing fossil-fuel boilers to biomass boilers in these states. In total, 3495 oil and coal boiler units in industrial and commercial buildings, and 1067 major wood energy facilities in the 37 eastern states were identified. These represent a subset of existing and potential conversions from fossil fuels to woody biomass. Based on this sample and energy consumption data from the Energy Information Administration (EIA), we estimate that there are currently 31,776 oil, coal, and propane boiler units over 0.5 MMBtus/hour capacity in these 37 states, representing a total energy consumption of 1.7 quadrillion Btus, or roughly the equivalent of 287 million barrels of oil. Were these units all converted to woody biomass fuel, they would consume a total of 121 million dry tons of wood per year, about three times the most recent US DOE estimates of woody biomass availability in those regions. Since only the most economical conversions typically occur, the reality of woody biomass market availability combined with thermal fossil-fuel consumption patterns suggests that roughly one-third of all potential projects could be achieved under sustainable utilization of existing biomass feedstocks in the three regions. Analysis of the results indicates that a targeted response to wood-conversion initiatives will yield the most successful program of fossil-fuel replacement in thermal applications. A ranking index developed in this study through analysis of existing boiler installations and availability of wood feedstocks suggests that the top ten states in the eastern United States on which to focus future messaging, feasibility studies, and policy development for potential woody biomass conversions are: 1. Maine, 2. Texas, 3. New York, 4. Florida, 5. Georgia, 6. Alabama, 7. South Carolina, 8. North Carolina, 9. Arkansas, 10. Pennsylvania. (C) 2013 Elsevier Ltd. All rights reserved.