Dear Mr. Sperry,
Thank you for posting your request on History Hub!
According to Reference Information Paper No. 91: Records Relating to North American Railroads, aerial photographs of track layouts and railroad structures may be located in Record Group 145. We searched the National Archives Catalog and located the Indexes to Aerial Photographs of the United States, 1953 - 1957 in the Records of the Farm Service Agency (Record Group 145) that include 3 file units and 17 items pertaining to Marshall County, KS. The items have been digitized and are available using the Catalog. For more information about the non-digitized records, please contact the National Archives at College Park - Cartographic (RDSC) at email@example.com.
Due to the COVID-19 pandemic and pursuant to guidance received from the Office of Management and Budget (OMB), NARA has adjusted its normal operations to balance the need of completing its mission-critical work while also adhering to the recommended social distancing for the safety of NARA staff. As a result of this re-prioritization of activities, you may experience a delay in receiving an initial acknowledgement as well as a substantive response to your reference request from RDSC. We apologize for this inconvenience and appreciate your understanding and patience.
We hope this is helpful. Best of luck in your family research!