The Cartographic Branch holds aerial imagery covering much of the United States and also many areas around the world. Today’s post will focus on getting started with aerial imagery covering the United States, and specifically, Record Group (RG) 145 imagery. For more information on locating foreign aerial photography, see our previous posts: Researching Foreign Aerial Photography and Researching Foreign Aerial Photography – Captured German Aerial Prints.
The bulk of Cartographic Branch’s aerial photography holdings dates from the 1930s to the 1950s, although some coverage is available outside of those dates. This aerial photography is held within four main record groups: RG 145, RG 114, RG 95, and RG 373. Coverage can also be found in some other record groups, which are included in the domestic aerial finding aid, Special List 25.
To get started researching aerials for an area in the United States, first check Special List 25. This finding aid, which is arranged by state and county, lists aerial coverage, including the coverage years, and the record group. It is available for download as a spreadsheet at the following link: Special List 25 – United States or is available to view and use in our research room.
To start, select the sheet tab at the bottom for the state. Next, look for the county. For our example, we will look at Van Wert County, Ohio.
Column A lists the County/Area. Column B lists the project symbol associated with the photography project. Column C lists the year. A “p” following the year means that there is partial coverage for that county and year. Column D lists the Record Group (RG). For Van Wert County (outlined in blue), there is coverage within RG 373, RG 145, and RG 57. RG 373 domestic imagery is located the same way as RG 373 foreign imagery using the overlay indexes that are available through the National Archives Catalog. See our post on Researching Foreign Aerial Photography for more information. RG 57 indexes are available to request and view in our research room.
The next step in the process is to locate your area(s) of interest on the aerial index sheet. Each aerial index sheet is a photo mosaic comprised of many small squares that represent individual photographic frames. The aerial indexes for RG 145 from the 1930s through approximately 1953 were recently digitized and are now available online through the National Archives Catalog. We are in the process of digitizing and making the index sheets from other record groups, including RG 114 and RG 95, available in the catalog as well. Indexes not available through our online catalog can be requested and viewed in person in our research room.
To locate the aerial indexes in our catalog for a particular county, we recommend using the advanced search option, and entering the county and state name, along with the term “aerial index” (example: Van Wert County Ohio Aerial Index) in the search term field, and then selecting File Unit for the Level of Descriptions field and National Archives at College Park – Cartographic Branch for the location of materials field. This search should yield results similar to the screenshot below:
Click on the year of interest. Then, under the details section, click on the blue hyperlink next to “includes.” This will take you to the individual sheet or sheets of aerial indexes. If no blue hyperlink appears next to includes, this means that these aerial index sheets are not yet available electronically in our catalog.
Each photographic exposure taken during the aerial photography project is shown as a square on the aerial indexes. Note that there is significant overlap between frames, so your area may be covered on more than one frame. Locate your area of interest on the aerial index sheets. You may need to compare the aerial index sheet to a topographical map in order to find your location. Remember that roads, highways, interstates, building, and other landmarks may have changed over time, especially from the 1930s to today.
In the upper corner of each square on the photomosaic index is the symbol, roll, and frame number. For our example, this information is BVO-7-18. BVO is the project symbol, 7 is the roll number, and 18 is the frame number. The symbol and roll number are required to locate the actual rolled aerial negatives.
After locating the roll and spot number, the next step is to check our Can Locators, which are available both electronically and as a hard copy in our research room. They are arranged by record group. Look up the symbol and roll number to determine which can of rolled aerial negatives contains the specific imagery. If the can is a “DN” can, that means that it is a duplicate and is available to request in our College Park research room as a normal pull. If the number is an “ON” number, that means it is an original negative and is stored off-site in cold storage for preservation reasons. ON cans need to be ordered and then can be viewed in our College Park research room. There is approximately a 3 business day delay before the film is available for use.
In our research room, we have light tables and aerial scanners that are available to view and copy aerial photography. More information about these options can be found on our post about Foreign Aerial Photography.
Cartographic reference staff are available daily to assist with aerial questions in person in our research room at the National Archives at College Park, Maryland.