Dear Mr. Linville,
Thank you for posting your request on History Hub!
National Archives’ Special Media Division recently announced on their blog, The Unwritten Record, that the file unit United States in the series titled Civil Works Map File, 1818 - 1947 in the Records of the Records of the Office of the Chief of Engineers (Record Group 77) has been digitized in full. To search this file unit, click here and then click on the blue “Search within this file unit.” Then remove the *:* from the search box at top and type in your keyword.
In addition to these maps, there are others from Record Group 77 which have been digitized and are available through the National Archives Catalog. The easiest way to find all the digitized maps in Record Group 77 is to go to our Record Group Explorer. Click on the box for RG 77 Chief of Engineers. Then click on Maps. Alternatively, you can do an Advanced Search. In the “Record Group Number / Collection ID” field put 77. In “Type of Archival Materials” select Maps and Charts. If you only want to see digitized maps, in the “Limit Search to:” field select Archival Materials Online. Then, in your search term, you can put in a key word such as the name of an area or place. Please review National Archives Catalog Search Tips for additional instructions.
While many maps in National Archives custody are available online, many more have yet to be digitized. For information about maps not yet available online, or for help with finding a specific map in the Catalog, please contact the National Archives at College Park - Cartographic (RDSC) via email at email@example.com. Their website is https://www.archives.gov/research/cartographic.
We hope this information is helpful. Best of luck with your research!