This rule establishes air quality designations for most areas in the United States (U.S.), including areas of Indian country, for the 2012 primary annual fine particle (PM<INF>2.5</INF>) National Ambient Air Quality Standards (NAAQS). Through these designations, the Environmental Protection Agency (EPA) is identifying as "nonattainment" those areas that are violating the 2012 PM<INF>2.5</INF> NAAQS based on quality-assured, certified air quality monitoring data from 2011 to 2013 or those areas that are contributing to a violation of the NAAQS in a nearby area. The EPA is initially classifying all nonattainment areas as Moderate. Also, through this final rule, the EPA is designating several areas as "unclassifiable" where the EPA cannot determine based on available information whether the area is meeting or not meeting the NAAQS or where the EPA has not determined whether the area contributes to a nearby violation. Additionally, the EPA is deferring initial area designations for several areas where the EPA cannot determine using available data whether the areas are meeting or are not meeting the NAAQS, but for which forthcoming data will likely result in complete and valid data needed to determine a designation. The EPA will assess these data as they become available and promulgate initial area designations for the deferred areas through a separate rulemaking action. The EPA is designating as "unclassifiable/attainment" all remaining areas of the country.