With recent shifts in public attitudes across the United States concerning the problem of global climate change, momentum is building for aggressive action to mitigate greenhouse gas emissions. At the same time, the ongoing economic recession presents challenges for financing an aggressive climate change abatement campaign; hence, it is imperative that cost-effective strategies for reducing greenhouse gas emissions be identified and pursued. To accomplish this, policy instruments will need to be tailored to a complex range of local and regional conditions. With these challenges in mind, we have assembled carbon budgets and evaluated mitigation opportunities for 9 counties in the Northeastern United States which vary widely in biophysical, demographic, political, and economic conditions. Most of the counties analyzed were net sources of CO2 to the atmosphere as emissions from fossil fuel combustion exceeded sequestration in vegetation and soils. The exceptions were the two most rural, forested counties in northern New Hampshire where sequestration in growing forests exceeded CO2 emissions. Thus, much of the northeastern United States is a source of atmospheric CO2 with the strength of the source varying primarily with human population density and only rural forested counties acting as net C sinks. We classified CO2 emissions across the region into four economic sectors: transportation (not including air travel), residential, commercial and industrial. On a per capita basis the transportation sector was the largest emissions source, followed by residential, commercial and industrial. Per capita emissions in transportation were similar across the various counties, the most notable exception being for Baltimore City, where per capita emissions were 44% lower than for the adjacent, suburban Baltimore County. The strategies with the most potential for carbon mitigation varied greatly across the counties. However, by implementing a range of locally tailored management and technology options, we can achieve substantial emissions reductions at the lowest potential cost.