"Pompeys Pillar in Montana was proclaimed a national monument in January 2001. Prior to its monument status, it was a designated national historic landmark in 1965. It is located along the Lewis and Clark National Historic Trail." | Source: Wick, Bob. "Pompeys Pillar." 29 September 2012. Wikimedia Commons. https://commons.wikimedia.org/wiki/File:Pompeys_Pillar_NM_(9424545304).jpgDownload Original File
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