The growth of the U.S. economy has been accompanied with a significant rise in carbon dioxide (CO2) emissions. As CO2 emissions are dependent on regional climatic conditions and energy-related activities in states, this study examines the extent to which the distribution of CO2 emissions vary across nine climatically consistent regions in the U.S. The results obtained from the entropy approach reveal that the inequalities of CO2 emissions vary across the regions. While the total inequality of CO2 emissions is determined by the between-region and the average within-region inequalities, the between-region inequality begins to dominate the average within-region inequalities around 1980s; the emission inequalities between regions increase, but those within each region decrease. Given that ethanol usage is relevant to energy-related CO2 emissions, this study also evaluates the impact of ethanol usage on the changes in the emission inequalities. The results show that an increase in the ratio of ethanol to fossil fuels is associated closely with the reductions in the inequalities of CO2 emissions.