Dear Mr. Windsor,
Thank you for posting your request on History Hub!
We searched the National Archives Catalog and located 2 series titled Burial Records of Civil War Volunteer and Regular Army Units, 1864-1870; and Civil War Burial Lists, 1865-1869 in the Records of the Office of the Quartermaster General (Record Group 92) may include burial records of members of the 91st Ohio Volunteer Infantry Regiment; and a series titled the 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 contains a file unit titled Regimental and Company Books of the 91st Ohio Infantry Regiment during the Civil War. The records are not digitized yet and available in the Catalog. For access to and/or copies of these records, please contact the National Archives at Washington - Textual Reference (RDT1) via email at firstname.lastname@example.org.
We also located a series titled Mathew Brady Photographs of Civil War-Era Personalities and Scenes, 1921-1940 in the Records of the Chief Signal Officer (Record Group 111) that may contain photographs of officers and soldiers of the 91st Ohio Volunteer Infantry Regiment. Some records are digitized and available in the Catalog but not all. For access to and/or selected copies of this series, please contact the National Archives at College Park - Still Picture (RDSS) via email at email@example.com.
In addition, we located a series titled Published Maps, 1820-1979 in the Records of the Office of the Chief of Engineers (Record Group 77) that may contain a map of the Battle of Fisher’s Hill. For access to and/or copies of this map, please contact the National Archives at College Park - Cartographic (RDSC) via email at firstname.lastname@example.org.
We suggest that you review Map of Battle Field of Fisher's Hill, Va.; Ohio History: Civil War; Ohio in the Civil War Genealogy; Battle of Buffington Island; Letters from the 91st OVI; Ohio Civil War Roster - Results; and Find A Grave websites for additional resources or answers to your questions.
We hope this is helpful. Best of luck with your family research!