Winrock International evaluated the potential for terrestrial carbon sequestration through afforestation in Shasta County, California.  The report presents suitability of rangelands for afforestation, potential carbon accumulation, total costs, and potential carbon supply, and also includes spatially explicit analyses illustrating attractive regions for afforestation within the county and the range of afforestation costs. Researchers determined that afforestation of Shasta County rangelands could result in the sequestration of about 17.7 million tons of carbon (t C) after 20 years at a cost of less than $20/t C ($5.45/ton of carbon dioxide [t CO2]) or about 57.6 million tons of carbon after 80 years at a cost of less than $10/t C ($2.7/t CO2).  This opportunity, which will be tested and validated through pilot projects in Shasta County under the U.S. Department of Energy‐funded West Coast Regional Carbon Sequestration Partnership (WESTCARB)—Phase II, could be replicated elsewhere in California and the WESTCARB region.  The report also provides a summary of initial outreach efforts to landowners interested in conducting afforestation for carbon.  The authors also include recommendations for further characterization and stratification, landowner outreach, and considerations for incorporating such projects into evolving voluntary carbon markets and regulatory programs.