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 Value81.41140 C.F.R. § 81.411Kentucky.Last amended: 2016Year: 2026Length: 15 wordsOfficial source Cite as 40 C.F.R. § 81.411 (2026)Area name Acreage Public Law establishing Federal land manager Mammoth Cave NP 51,303 69-283 USDI-NPSPrevious40 C.F.R. § 81.410Next40 C.F.R. § 81.412