Look for your ancestors in the 1850 and 1860 slave schedules (a separate part of the US Census for those years). These schedules list the slave owners' names, and the the age, gender, & color of each of their slaves. The names of slaves are almost always not listed.
Dear Mr. Barbieri,
Thank you for posting your request on History Hub!
To supplement the information from the previous poster, we searched the National Archives Catalog and located Population Schedules for the 1850 Census (including slave schedules) and the Population Schedules for the 1860 Census (including slave schedules) in the Records of the Bureau of the Census (Record Group 29) that may contain information about the slave holding status of your ancestors. 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.
As records of enslaved people were often listed as property or estate transactions, we suggest that you request a search from the Library of Virginia for tax lists, probate and deed records for your ancestors. In addition, the NARA document Federal Records that Help Identify Former Slaves and Slave Owners and the FamilySearch Research wikis for Virginia Land and Property and Virginia Probate Records may be useful.
We hope this is helpful. Best of luck with your family research!