At the risk of being accused of beating a dead horse, here is another relevant nugget about whether African Americans fought at the First Battle of Bull Run/Manassas on July 23, 1861. (Click on the links to read the first three posts of this thread: 1) July 27; 2) July 28; 3) August 1.) The following short article appeared in the September 12, 1861 issue of The Weekly Anglo-African, under the title, ”A Colored Soldier at Bull Run.”
When Governor Sprague’s battery was about to leave Providence for Washington a few months ago, the officers wished to engage the services of a colored citizen of that state as a servant. He replied that he was perfectly willing to go, but would only go as the rest went a full private in the corps. After a little demurring, he was regularly enlisted as a volunteer. At the Battle of Bull Run, the Captain of his guns was killed early in the action, and the colored soldier took command and held it to the last moment; for which he was highly complimented on the return of the troops to Providence. The name of the hero is Mr. James Reeder. Pass him round.
The article has some credibility, because James Reeder’s name can be found in the National Park Service’s Soldiers and Sailors System as a member of the 1st Rhode Island Light Artillery. (It is also not a common enough name to likely be a coincidence.) However, an account of this unit at the First Battle of Bull Run/Manassas by J. Albert Monroe, then a Captain in the 1st Rhode Island Light Artillery, rising later to Lt. Colonel, does not mention a captain being killed during the battle or any heroics by James Reeder.
Still, it is significant that an African American in all likelihood served as a mustered-in soldier of a ninety-day company at the first major battle of the Civil War. While it does not change the basic story of black men’s initial exclusion from the Union army, it does show exceptions existed, especially very early on when both armies still were learning their business. The evidence presented in this thread of Civil War Emancipation suggests that most of the (small number of) black men that apparently fought at First Bull Run/Manassas did so unofficially, ostensibly with the Union and Confederate armies as servants or laborers, but it is interesting in the case of James Reeder that he was a fully mustered-in soldier.
Sources: The Weekly Anglo African, 12 September 1861, http://research.udmercy.edu/find/special_collections/digital/baa/item.php?record_id=1303&collectionCode=baa; Civil War Soldiers and Sailors System, http://www.itd.nps.gov/cwss/; J. Albert Monroe, The Rhode Island Artillery at the First Battle of Bull Run (Providence, R.I.: Sidney S. Rider, 1878), http://www.archive.org/stream/rhodeislandartil00monr#page/n7/mode/2up.