Dear Mr. Barrows,
Thank you for posting your request on History Hub!
Census records for 1790 through 1860 may indicate the number of enslaved persons in the households of the mill owners. See Search Census Records Online and Other Resources for information about accessing these records. Please email the National Archives at Washington, DC - Textual Reference (RDT1) at Archives1reference@nara.gov for questions about census records.
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 RDT1. We apologize for this inconvenience and appreciate your understanding and patience.
The census records have been digitized by Ancestry. In response to the COVID-19 pandemic, the National Archives has partnered with Ancestry to make the vast majority of their NARA-digitized holdings freely available to the public. Anyone with Internet access may create an account, access NARA records, and use other Ancestry resources, such as their educational offerings and family tree-maker application. For more information see Ancestry’s announcement -- “Free At-Home Education Resources From Ancestry® and Access to Nearly 500M National Archives Records”.
The State Archives of North Carolina has nonpopulation censuses for North Carolina for 1850 and 1860 which may provide information about specific gristmills, and they may have additional records concerning slavery in North Carolina. The State Library of North Carolina may also be able to assist you. Their How to find slave records page focuses on research for genealogical purposes, but some of the suggestions may be useful for your research. We suggest that you contact both of these institutions for information about their holdings on this topic. They may have suggestions for other places to research as well.
You also may wish to contact local and state historical societies, museums, county courts, university libraries, and similar repositories which may have information about specific grist mills and/or slavery in a given locaility. Also, the Society for the Preservation of Old Mills may have information about slavery and mills and advice regarding researching specific mills.
Finally, in regards to American grist mills in general, we suggest that you contact the Fred W. Smith National Library for the Study of George Washington. Although they are unlikely to have information on specific grist mills in North Carolina, they have information on George Washington’s grist mill that is a notable example of a grist mill where slave labor was used. Their staff also may be able to make additional recommendations concerning researching colonial and early American mills and slavery.
We hope this information is helpful. Best of luck with your research!