It is widely accepted that there is a definite link between air pollution and asthma, a disease that the CDC estimates costs the U.S. Economy over $80 billion per year (ATS, 2018). Concerns about these economic and human costs have resulted in environmental policies such as the Clean Air Act. However, some localities still suffer from elevated air pollution. To investigate the impact of such pollution on asthma, we study county-level data on air quality and asthma hospitalizations for the state of California from 2015 to 2018. After controlling for a variety of county-level characteristics, we find that higher concentrations of carbon monoxide (CO) increase the number of hospitalizations due to asthma at the county level. This suggests that policies to reduce fossil fuel emission sources such as electric vehicle subsidies and tax credits, as well as policies to ensure equitable access to asthma mitigation medication such as universal healthcare still have the potential to decrease asthma hospitalizations.