US lawFederal (United States)RegulationsTitle 40 CFR — Protection of EnvironmentChapter I — ENVIRONMENTAL PROTECTION AGENCYPart 81 — DESIGNATION OF AREAS FOR AIR QUALITY PLANNING PURPOSESSubpart D — Identification of Mandatory Class I Federal Areas Where Visibility Is an Important Value81.42440 C.F.R. § 81.424Oklahoma.Last amended: 2016Year: 2026Length: 15 wordsOfficial source Cite as 40 C.F.R. § 81.424 (2026)Area name Acreage Public Law establishing Federal land manager Wichita Mountains Wild 8,900 91-504 USDI-FWSPrevious40 C.F.R. § 81.423Next40 C.F.R. § 81.425