This primary source comes from the Records of the Office of the Chief of Engineers.
National Archives Identifier:
305587Full Citation: Reconnaissance of the Battle field at Bull Run, Va., fought July 21, 1861. Made on March 14, 1862, by Henry L. Abbot, 1st Lieut., Top. Engineers.; 3/14/1862; Records of the Office of the Chief of Engineers, Record Group 77. [Online Version, https://www.docsteach.org/documents/document/reconnaissance-of-the-battle-field-at-bull-run-va-fought-july-21-1861-made-on-march-14-1862-by-henry-l-abbot-1st-lieut-top-engineers, May 5, 2024]