The Environmental Protection Agency (EPA) is approving a regional haze state implementation plan (SIP) revision submitted by the State of Montana on August 10, 2022 (Montana's 2022 SIP submission), as satisfying applicable requirements under the Clean Air Act (CAA) and the EPA's Regional Haze Rule (RHR) for the program's second implementation period. The EPA is also finalizing approval of the prong 4 visibility portion of Montana's October 1, 2018, Infrastructure SIP submission for the 2015 ozone National Ambient Air Quality Standard (NAAQS). The EPA is taking this action pursuant to the CAA.