Historical Topographic Maps
Georeferencing means that the internal coordinate system of a map or aerial photo image can be related to a ground system of geographic coordinates.
USGS Digital Raster Graphics (DRGs) were created in the period 1995-2000. They were 250 dots-per-inch scanned images of what were then the most current editions of topographic maps (approximately 58,000 maps).
Superseded US Topo maps will remain available for download, but will not become part of the Historic Topographic Map Collection (HTMC).
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