Historical Maps -- Frequently Asked Questions
How many USGS topographic maps are included in the Historical Topographic Map
- The USGS is scanning all editions and all scales of topographic maps produced
since the inception of the topographic mapping program in 1884. The exact number of
maps is unknown at this time since an accurate catalog does not exist. 200,000 is the
number currently being used until an accurate count of the scans can be made. All 50 States,
Puerto Rico and Trust Territories are included in the effort to complete the collection.
- What scales of maps are included in this collection?
- Map sheets were initially published at three primary scales 1:62,500; 1:125,000; and 1:250,000 scale with contour intervals of 10, 20, 50, 100 or 200 feet depending on the terrain. In terms of scale and latitude and longitude, these map specifications were expanded to include the scales and geographic extents in the following table:
Map scale (series)
1:24,000 (7.5 x 7.5 minutes)
1:25,000 (7.5 x 7.5 minutes)
1:25,000 (7.5 x 15 minutes)
1:31,680 (7.5 x 7.5 minutes)
1:48,000 (15 x 15 minutes)
1:62,500 (15 x 15 minutes)
1:63,360 (15 x 15 minutes)
1:100,000 (30 x 60 minutes)
1:125,000 (30 x 30 minutes)
1:250,000 (1 x 1 and 1 x 2 degrees)
Another way of looking at maps scales for specific areas is:
- 7.5-minute maps of the conterminous United States, Hawaii, and limited areas of Alaska at
1:24,000 and 1:25,000 scale.
- 7.5 x 15-minute maps in limited areas of the conterminous United States at 1:25,000 scale.
- Pacific Island maps at 1:20,000, 1:24,000, and 1:25,000 scales.
- Puerto Rico and the Virgin Islands at 1:20,000 scale.
- Culebra, its adjacent islands, and the Island of Vieques at 1:30,000 scale.
- Alaska at 1:63,360 scale.
- 30 x 60-minute maps of the conterminous United States at 1:100,000 scale.
- 1 x 2-degree maps of the United States at 1:250,000 scale.
These first map sheets, usually at the scale of 1:125,000, were engraved in copper with the hydrography (water) printed in blue; hypsography (contours) in brown; the projection lines, lettering and other cultural features in black. The scale of 1:62,500 prevailed until the 1950's, when a requirement for more detailed maps resulted in a change to the standard scale of 1:24,000. Map seekers will find other editions available at 1:31,680 and 48,000-scale.
- When was the topographic map series for the conterminous 48 States, Hawaii, Alaska
and Territories completed?
- The USGS completed the primary topographic map series of the conterminous United States at the scale of 1:24,000 in 1992. Revisions were made until 2006. Alaska, Hawaii, Puerto Rico and Territories were done at other scales and will be included in the collection.
- How will digital copies of the historical maps be made available to the public?
- The GeoPDF file format is free to download from the USGS Store at
(http://store.usgs.gov/). The average file size is about 12 MB per map. Plans are underway
to offer the map in GeoTIFF format and be available from The National Map Viewer at
Average file size will range from 600 MB to 1.2 GB per map.
- How will printed copies of the be made available to the public?
- Printed copies can be ordered at the store.usgs.gov or by calling 1-888-275-8747 (1-888-ASK-USGS) option 1. Maps are $15.00. Major credit cards are accepted and a $5 handling fee is applied to all orders.
- How will it be known when a particular historical map has been scanned and is available for download?
- The index of available quads is located on the website at http://nationalmap.gov/historical/status.
- A set of the original historical topographic maps reside in the archives of the USGS
Library in Reston, VA. This is the largest repository of this collection; however it is
known that this collection is not complete. What process is the USGS using to identify
and obtain copies of missing maps to assure a complete collection?
- As the maps are scanned, a comprehensive catalog is being developed. The catalog will be
shared and cross referenced with the collections held by the USGS Library. In some instances,
State Repository Map Libraries, the Library of Congress and other repositories will be
contacted and their holdings assessed.
- Are metadata available?
- Yes. FGDC-compliant metadata will accompany each map.
- What is metadata?
- Metadata, as described by the Federal Geographic Data Committee, is "the background information which describes the content, quality, condition, and other appropriate characteristics of the data. Paper maps contain metadata, primarily as part of the map legend. In this form, metadata is readily apparent and easily transferred between map producers and map users. When map data are in a digital form, metadata is equally as important, but its development and maintenance often require a more conscious effort on the part of data producers and the chain of subsequent users who may modify the data to suit their particular needs." This collection has gathered all dates and other relevant information from the printed maps and included the data in a metadata file for each map.
- What is the definition of the word 'georeferenced'?
- Georeferencing means that features on the historical maps are tied to the Earth's
coordinate system using latitude and longitude. Georeferencing then allows the historic
quadrangles to be used in a GIS system and combined with other data. Users who download
and install the free TerraGo toolbar extension to Adobe Reader
(http://www.terragotech.com/products/terrago-toolbar) will see an interactive coordinate
display as they move their mouse across the GeoPDF image.
- Map symbology has changed through the years. Where can one find the correct map
symbology for a particular historical map?
- At this time there is no compiled symbology used for the various scales during different
eras. The latest symbology used for the 7.5 minute series can be found at
- Why are some of the maps yellowed or have extra stamps or marks?
- The goal of this collection is to find, catalog and georeference all topographic maps published by the USGS. The intent is to allow complete access to the content of these maps so the history documented by this collection and the analysis of distribution and spatial patterns is available throughout the sciences and non-science disciplines. Genealogists, historians, anthropologists, archeologists and others
will use this collection for research as well as for a framework on which a myriad of information can be presented in relation to the landscape. Maps are scanned and georeferenced in an "as is" condition and restoration for removing yellowing or other extraneous marks is beyond the scope of effort to create this Collection. The full resolution files will be made available in 2012 if an individual wants to edit the files to restore the image more closely to the original printed quality.
- You state the first release of maps for a State as "standard cells", and "nonstandard maps" will be released as part of a second phase. What does this mean?
- The USGS topographic maps are best known as "quadrangles". The quadrangle maps normally cover a standard unit of latitude and longitude. An example is the 1:24,000 maps that are 7.5 x 7.5 minutes. Question 2 provides a complete list of the different geographic extent of USGS quadrangles. Occasionally maps were prepared and printed with a slightly different geographic area to allow the map to extend to a State border or include a geographic feature (island, peninsula, etc.) to make the map more useful to the reader. These require additional processing and are been done in a later, separate process. Nonstandard maps will be available in 2012.
- It appears there are multiple copies of the same map as they all have the same date. Is there a difference?
- Yes, these are different maps. After the initial preparation and printing maps are either reprinted or revised before a new printing. The date used to identify a map is the larger date in the lower-right corner. If there are multiple editions with the same "Date on Map", it is suggested you look at the other date(s) available. A short definition of each is provided below:
|Date on Map
||The year the map was created
||The year the map was printed
|Photo Inspection Year
||The year when a photo inspection was last done on the map
|Photo Revision Year
||The year when photos were used to revise a map
|Field Check Year
||The year map content was verified in the field
||The year when a field survey was completed for the mapped area
||The year the map was last globally edited or revised
Sometimes there are visual differences between two maps that cannot be captured or determined by different dates. Examples are special editions printed with or without woodland (green) tints. It was decided to include all editions with any visual differences in metadata or map content in order to be comprehensive. The user is invited to select the edition best meeting their need.
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