Map symbology has changed through the years. Where can I find the symbol key for a particular historical map?
There is no single document that describes all symbols used on all USGS topographic maps. Following is a summary of documents and standards, both current and historical, that are available online from the USGS Publications Warehouse and USGS National Geospatial Program web sites. These documents together form a fairly complete description of topographic symbols from about 1900 to the present, though it is possible that some unusual symbols are not in any published document.
7.5-minute maps, circa 1947-present
The following document was last updated in 2003, but its lineage goes back to 1958. It describes map symbols for most maps of the 7.5-minute program in the second half of the 20th century:
Summary pamphlet (2005), which includes symbols for "Provisional Maps" of the 1980s:
- Citation page: http://pubs.er.usgs.gov/publication/70039164
In the early 1990s modified symbols were defined. This symbol set was intended to be more friendly to digital map production. Only a few thousand maps were published with these symbols.
Most current US Topo maps (2013-present) have a PDF symbol pamphlet attached to each map file. This pamphlet is also posted here.
Other Map Series, circa 1900-2000
Topographic Standards (1918):
- Citation page: http://pubs.er.usgs.gov/publication/70039569
- Report: http://pubs.usgs.gov/unnumbered/70039569/report.pdf (Symbols begin on PDF page number 223)
Topographic Standards (1928):
- Citation page: http://pubs.er.usgs.gov/publication/b788E
- Report: http://pubs.usgs.gov/bul/0788e/report.pdf (Symbols begin on PDF page 130. To find other chapters of this publication, go to http://pubs.er.usgs.gov/ and search on "topographic instructions")
1:50,000-scale 15-min maps (1980):
- Citation page: http://pubs.er.usgs.gov/publication/70101777
1:100,000-scale maps (1993):
Various standards and technical documents are posted on the National Geospatial Program standards page. Some documents on this site are for current projects and products, others are from legacy projects of the late 20th century. The page also includes links to important non-USGS geospatial standards.