On June 1, 1861, a Union scouting party clashed with the local militia in Fairfax, Virginia, resulting in the war's first deaths in action, and the first wounding of a field-grade officer.

Marr rallied his unit, but was killed, and command was taken over by a civilian ex-governor of Virginia, William Smith, who forced the Union to retreat.

The Union did not gain the intelligence it was seeking, and had to delay its drive on Richmond, thus enabling the Confederates to build up their strength at Manassas in advance of the much-bigger battle there, the following month.

On April 15, 1861, the day after the surrender of Fort Sumter in the harbor of Charleston, South Carolina to Confederate forces, President Abraham Lincoln called for 75,000 volunteers to reclaim federal property and to suppress the rebellion begun by the seven Deep South states, which had formed the Confederate States of America (Confederacy).

[1] Four Upper South States, including Virginia, refused to furnish troops for this purpose and began the process of secession from the Union with the intent of joining the Confederacy.

[9] Confederate Lt. Col. Richard S. Ewell, who had recently resigned as a captain of cavalry in the United States Army was in command of this largely untrained and ill-equipped force.

[9] On the night of May 31, only two pickets were posted on the road east of town because little threat of attack from Federal forces who were no closer than 8 mi (13 km) away was expected.

[10][11] On the same day, Brigadier General David Hunter gave verbal orders to Lieutenant Charles Henry Tompkins of the 2nd U.S. Cavalry Regiment to gather information about the numbers and location of Confederate forces in the area.

[15] Captain Marr moved his men into a clover field west of the Methodist church where they had been camped, just off Little River Turnpike, and formed them into two battle lines.

Whether he had moved up to challenge the Union riders or to scout out a better position for his company as some accounts suggest, Marr was not in the immediate presence or line of sight of any of his men on the very dark night when he fell in the dense field.

[15] According to many of the accounts of the battle, the Union troopers fired at a man emerging from the hotel in town, who happened to be Lt. Col. Ewell, and wounded him in the shoulder.

[21] After the initial flurry of activity, the flight of the Prince William cavalrymen and the ride on through town by the Union force, the men of the Warrenton Rifles infantry company realized that Captain Marr was no longer present.

Ewell then placed the approximately 40 men of the Warrenton Rifles that he found at the edge of the clover field between the hotel and the courthouse (or the Episcopal Church).

[25] where they were able to turn the Union force back to the west with a volley as the cavalrymen approached the Confederate position on their return trip through town.

[24] The Confederates fired additional volleys at the Federals as they tried to pass through town again on their way back to their base at Camp Union near Falls Church, Virginia.

[31] The Confederates initially reported casualties in the affair of one dead (Captain Marr), four (later reduced to two) wounded (including Lt. Col. Ewell) and one missing.

[42] Although this battle faded into insignificance after larger Civil War battles with many more casualties were fought, it was notable in several respects, including the occurrence of the first Confederate combat casualty of the war, the first wounding of a field grade officer, an eventual award of a Medal of Honor for actions at the first combat for which the award was given, the failure to discover the Confederate buildup at Manassas Junction, the delay in Union Army action caused by the inflated report of Confederate strength in the area and the foreshadowing of the thousands of actions of similar type and scale that would occur during the course of the war.

It reads: "This stone marks the scene of the opening conflict of the war of 1861–1865, when John Q. Marr, captain of the Warrenton Rifles, who was the first soldier killed in action, fell 800 feet south, 46 degrees West of the spot.