This report on Clean Air Act (CAA) major sources provides summary data on source universe as well as the compliance monitoring activities and enforcement actions by the United States Environmental Protection Agency (EPA), states, tribal and delegated local agencies. A major source has actual or potential emissions above at least one of the applicable major source thresholds, which are: 100 tons per year for any air pollutant other than greenhouse gases; 10 tons per year for any single hazardous air pollutant (HAP), or 25 tons per year for any combination of HAPs; or 10 to 250 tons per year for criteria air pollutants, depending on the area's air quality attainment status. The time frame of this report is the 2009 federal fiscal year (FY09), which extends from October 1, 2008, to September 30, 2009. The data provided in this report are from EPAs Air Facility System (AFS). AFS is the national database of record for CAA compliance and enforcement data for stationary sources regulated by EPA, state, tribal and local air pollution agencies. The data was pulled from AFS in March 2010.