This primary source comes from the Records of the Environmental Protection Agency.
National Archives Identifier:
544073Full Citation: The View of Phoenix's Urban Sprawl from 4000 ft. South Mountain in background.; 06/1972; Records of the Environmental Protection Agency, Record Group 412. [Online Version, https://www.docsteach.org/documents/document/the-view-of-phoenixs-urban-sprawl-from-4000-ft-south-mountain-in-background, April 20, 2024]