Dear Mr. Shaw,
Thank you for posting your request on History Hub!
We searched the National Archives Catalog and located the series Carded Records Showing Military Service of Soldiers Who Fought in Volunteer Organizations During the American Civil War in the Records of the Adjutant General's Office, 1762 - 1917 (Record Group 94) that includes the compiled military service record (CMSR) for Harold, John - Age 24, Year: 1863 - Fourth Infantry. This file has been digitized and is available online using the Catalog.
Additionally, there may be a pension file for him in one of several series, though please note that not all Civil War veterans received pensions. The majority of Civil War pension files in the Records of the Department of Veterans Affairs (Record Group 15) are in the custody of the National Archives at Washington, DC - Textual Reference (RDT1). There are also 3 record series (XC files) in Record Group 15 at the National Archives at St. Louis (RL-SL) that include claims files relating to Civil War Veterans. These records were transferred to the National Archives in 1952 and 1955 from the VA. Please email both RDT1 at Archives1reference@nara.gov and RL-SL at firstname.lastname@example.org with full details to request a search for a pension file.
We also located Regimental and Company Books of Civil War Volunteer Union Organizations, 1861 - 1867 in the Records of the Adjutant General's Office, 1762 - 1917 (Record Group 94) that includes the Regimental and Company Books of the 4th Tennessee Infantry Regiment. Please contact RDT1 for more information.
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 and RL-SL. We apologize for this inconvenience and appreciate your understanding and patience.
We hope this is helpful. Best of luck with your research!