In this document, the Environmental Protection Agency (EPA or Agency) is taking three separate but related actions. First, EPA is finalizing its determination that the Libby fine particulate matter (PM<INF>2.5</INF>) nonattainment area (Libby Area) is attaining the 1997 Annual PM<INF>2.5</INF> national ambient air quality standards (NAAQS or standard) based on 2014-2021 data. Secondly, EPA is finalizing approval of Montana's plan for maintaining the 1997 Annual PM<INF>2.5</INF> NAAQS (limited maintenance plan). Lastly, the EPA is finalizing approval of the redesignation of the Libby Area to attainment for the 1997 Annual PM<INF>2.5</INF> NAAQS, submitted by the State of Montana on June 24, 2020. The EPA is taking this action pursuant to the Clean Air Act (CAA).