It is unclear if recent policies and regulations regarding mercury emissions have resulted in significant declines in atmospheric mercury concentration and deposition into North American ecosystems. Regional and national deposition patterns are influenced by physical processes but also differing rates of mercury emissions partially due to variations in regulation. This book examines long-term trends in mercury deposition data collected by the North American Deposition Program (Mercury Deposition Network). Specifically, 16 sites across North America were analysed for spatial trends in mercury concentration in precipitation and per area wet deposition over ten years. An exploration of individual state mercury reduction initiatives and regulatory policies of North Carolina and Minnesota is presented. The analyses in this book should be useful to researchers examining the regional and global distributions of mercury and regulatory policy. This work is particularly important given the current initiatives to develop an international policy instrument for reduction of mercury emissions.