The Geological Survey is making a topographic and geologic map of the United States. The topographic map is being published in separate sheets and the geologic map in parts called folios. Each folio includes a topographic map and geologic maps of a small area, together with explanatory and descriptive text. Beginning with No. 164 the geologic folios are issued in two forms, the octavo or field edition and the folio or library edition.
Additional publication details
USGS Unnumbered Series
The topographic and geologic atlas of the United States