Breathing in ground-level or tropospheric ozone can trigger a variety of health problems including chest pain, coughing, throat irritation, and congestion. It increases problems with bronchitis, emphysema, and asthma. The ability to determine the impact of ozone precursor emission controls on ground-level ozone trends is complicated by the impact of meteorology, which can be either conducive to ozone formation or not. How do you know if emission controls are really working? The major precursors to ground-level ozone formation are volatile organic compounds (VOCs) and nitrous-oxides (NOx). The EPA Nitrogen Oxides State Implementation Plan Call (NOx SIP Call) began in 2001 in an effort to mitigate the formation of ground-level ozone. Since ozone is strongly affected by the influence of meteorological variables, many different approaches have been taken to determine the trend in ozone by removing the effects of varying meteorology. The purpose of this project was to build a time series model that removes the effects of meteorology, autocorrelation, and seasonal trends based on ozone and meteorological data from the Maryland and New Jersey Departments of the Environment. This data spans April through October of 1997-2006 for Maryland and Washington, DC and 1997-2005 for New Jersey. As the result of our analysis, a series of models were combined with a filtered time series model and back trajectory modeling to estimate the reduction in ground-level ozone over this ten-year period. These results suggest an improving trend in ozone concentrations over this time period in New Jersey and Maryland.