At 9 a.m. on the morning of July 18, 1861, the vanguard of Brigadier General Irvin McDowell’s Union army arrived at Centreville having met no organized Confederate opposition. Southern troops had fallen back to defensive positions behind Bull Run the night before. Acting under orders to “Observe well the roads to Bull Run and to Warrenton; Do not bring on an engagement, but keep up the impression that we are moving on Manassas,” General Daniel Tyler, commanding McDowell’s First Division, proceeded to make a reconnaissance towards Blackburn’s Ford. A squadron of cavalry and two companies of infantry from Colonel Israel Richardson’s brigade led the advance.
 

A Confederate brigade under General James Longstreet, consisting of Virginia and North Carolina infantry regiments and supported by seven guns of the famed Washington Artillery of New Orleans, stood poised to meet the Union advance at Blackburn’s Ford. Longstreet’s troops remained largely concealed by the woods along Bull Run. General P.G.T. Beauregard, commander of Confederate forces at Manassas since June 1^st, moved closer to the coming action and made his headquarters at Yorkshire, the nearby home of Wilmer McLean. McLean’s barn would serve as a Confederate field hospital during the battle.

By late morning Tyler was in a position overlooking Blackburn’s Ford on Bull Run. Although he observed a Confederate battery across the run, rebel troops could not be detected in any strength. “Desiring to ascertain the extent of [the Confederate] force,” Tyler called forward his artillery and Richardson’s entire infantry brigade, composed of the 1^st Massachusetts, 12^th New York, 2^nd Michigan and 3^rd Michigan, the latter two regiments being deployed facing Mitchell’s Ford.

Tyler’s guns opened fire shortly after noon but received no appreciable response. Determined to feel out the enemy, Tyler directed Richardson to advance a line of skirmishers. Upon approaching the wooded stream banks, a gray clad battalion from the 1^st Massachusetts drew scattering shots from skirmishers of the 1^st Virginia Infantry. In response, Tyler sent forward a section of 12-pounder field howitzers from Romeyn Ayres’ battery with a squadron of cavalry for support. Richardson also directed the 12^th New York and 1^st Massachusetts to move forward in support of the artillery pieces.  As the two howitzers opened fire the entire stream bottom erupted with heavy volleys of musketry. The New Yorkers became heavily engaged, yet fell back in disorder shortly thereafter, dangerously exposing the left flank of the 1^st Massachusetts. Captain Ayres recalled his exposed pair of howitzers after they had expended all of their canister rounds and some spherical case shot.  

Satisfied that the enemy was present in strong force, Tyler ordered Richardson’s battered infantry to disengage and withdraw. Ayres’ six guns, assisted by two 20-pounder Parrott rifles, kept up a steady but ineffective artillery exchange with Confederate batteries until 4p.m. In the course of one hour, Union artillery fired a total of 415 shots, while Confederate cannon returned 310 rounds. During this exchange a Union Parrott shell reportedly struck the chimney of Mr. McLean’s detached kitchen and the resulting debris destroyed a meal being prepared for General Beauregard. 

General Tyler reported 83 casualties while General Beauregard noted a total of 68 killed and wounded in this relatively small affair. Two soldiers in Company K, 12^th New York (Cpl. James E. Cross and Pvt. Charles F. Rand) would later be awarded the Medal of Honor for refusing to retreat at Blackburn’s Ford. The disorderly withdrawal of many Union troops, however, contributed to the perception of a Confederate victory, and left southern troops flushed with confidence. Although General McDowell severely criticized Tyler for aggressively exceeding his orders, the Union repulse at Blackburn’s Ford did yield valuable information to the Union commander. The sharp firefight revealed that the Confederate position along this stretch of Bull Run was formidably defended, and this knowledge contributed to McDowell’s decision to focus the Union efforts elsewhere along the Confederate line. Yet the Battle at Blackburn’s Ford would serve only as a minor prelude to greater bloodshed and a much more decisive defeat for Union forces just a little further upstream on July 21, 1861.