Dear Ms. Anthony,
Thank you for posting your request on History Hub!
We searched the National Archives Catalog and located the Population Schedules for the 1790 Census, Population Schedules for the 1800 Census, and the Population Schedules for the 1810 Census in the Records of the Bureau of the Census (Record Group 29) that may contain information about the Mitchell family in Unionville, Pennsylvania. Some of these schedules have been digitized in part. 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.
You may wish to search Ancestry.com for the U.S. Census. There may be a fee for using Ancestry. Instead, some of the images from Ancestry are available for free on Family Search or at your local library. Many library systems subscribe to these sites, making them free for their patrons.
We hope this is helpful. Best of luck with your research!