Dear Ms. Blair,
Thank you for posting your request on History Hub!
We searched the National Archives Catalog and located the Population Schedules for the 1860 Census, the Population Schedules for the 1870 Census, the Population Schedules for the 1880 Census, the Population Schedules for the 1890 Census; the Population Schedules for the 1900 Census, and the Population Schedules for the 1910 Census, the Population Schedules for the 1920 Census, the Population Schedules for the 1930 Census, and the Population Schedules for the 1940 Census in the Records of the Bureau of the Census (Record Group 29) that may contain information about Jefferson P Blair, Sr. The 1940 Census schedules are digitized and available using the Catalog. For access to the non-digitized schedules, please contact the National Archives at Washington, DC - Textual Reference (RDT1) via email at firstname.lastname@example.org.
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.
For information about the U.S. Census, see the Census Bureau technical documentation and questionnaires as well as NARA’s page on Census Records.
You may wish to search Ancestry.com or FamilySearch.org for the U.S. Census. There may be a fee for using Ancestry. Instead, please check for access at your local library as many library systems subscribe to these sites, making them free for their patrons.
We also suggest that you review NARA’s Resources for Genealogists, as well as the FamilySearch Research wiki for United States Genealogy. In addition, the document Suggestions and Advice for Family History Researchers may be useful.
We hope this is helpful. Best of luck with your research!