The 17th Virginia Infantry was organized at Manassas Junction in June 10, 1861. It was composed of ten companies, many of which began as prewar volunteer militias. The volunteers were from Alexandria, Fairfax, Fauquier, Loudoun, Prince William, and Warren Counties.

The core of these volunteers were four companies organized on February 18, 1861 as a volunteer militia battalion. The Mount Vernon Guard, Alexandria Riflemen, Old Dominion Rifles, and the Alexandria Artillery were attached to the 175th Regiment (Alexandria County), Virginia Militia. On April 2, the General Assembly passed an act authorizing a battalion be raised in the city of Alexandria with three companies of infantry and one of artillery. On April 4, Captain Montgomery Dent Corse, of the Old Dominion Rifles was unanimously elected to command the battalion as a Major.

The oldest company, the Mount Vernon Guard, was organized on June 21, 1842, but always observed July 4 as their anniversary. The first time they probably appeared in uniform was in October 1842 when the passed in review before President Tyler.

The Alexandria Riflemen were organized on March 10, 1856. Originally choosing the name "Alexandria Sharp Shooters", they quickly reconvened their meeting when some realized how the initials would look painted on the back of their knapsacks. The change of name to "Alexandria Riflemen" was unanimous. They were organized, with the Mount Vernon Guard, into a volunteer battalion under the command of Major Turner Wade Ashby. Ashby had been a lieutenant in Capt. Corse's company during the Mexican War.

The Old Dominion Rifles was organized on December 6, 1860. Organization was complete by January 7, 1861 with the election of Corse as captain and Arthur Herbert as lieutenant.

The Alexandria Artillery was formed in 1850 as the Mechanical Artillery. The new name was adopted in 1856.

The battalion went on active duty soon after the Ordinance of Secession was passed on May 23. Two companies of Irish citizens of Alexandria were added to the battalion on April 25, 1861--an artillery company, the Irish Volunteers, and a light infantry company, the Emmett Guards. Two Fairfax County cavalry companies joined the battalion, as well--the Chesterfield Troop and the Fairfax Cavalry, known also as the Washington Home Guard.

Before the end of April, three more companies were attached to Corse's command at Alexandria:

On April 24, the 80 men of the Loudoun Guard arrived from Leesburg and went to quarters at Tennesson's old restaurant on Cameron Street. The light infantry company was organized early in November, 1859 by Capt. Charles B. Tebbs. They were attached to the 57th Regiment (Loudoun County), Virginia Militia.

The Fairfax Rifles had been formed at Fairfax Court House by Capt. William H. Dulany on December 1, 1859 as the Fairfax Rifle Rangers and attached to the 60th Regiment (Fairfax County) Virginia Militia. James W. Jackson was an early member of the 60th Militia before moving to Alexandria to become the co-proprietor of the Marshall House. The Fairfax Rifles joined Corse under the command of Lt. William A. Barnes on April 25, 1861 and were assigned to barracks on Prince Street, near Fairfax Street.

Capt. Robert H. Simpson, a teacher, organized the Warren Rifles in Front Royal. In early 1860, the graduate of VMI attached the Rifles to the 149th Regiment (Warren County) Virginia Militia. The company marched to Winchester on April 18, 1861 to enroll for active service. From there, they proceeded by rail to Harpers Ferry. Ordered to Alexandria to escort a shipment of captured arms, they stopped at Front Royal and arrived in Alexandria on April 26. They were quartered on the north side of Cameron Street, between Fairfax and Royal Streets.

By April 27, Corse's command was designated as the Sixth Battalion of Virginia Volunteers under Lt. Col. Algernon S. Taylor. The native of Alexandria was commissioned in the Provisional Army of Virginia and was the nephew of former President Zachary Taylor.

On May 3, the battalion took an all night train ride from the Orange and Alexandria station to the Culpeper Court House sixty miles away. When they discovered an error by a telegraph operator, who wrote "Battalion" instead of "Battery," they returned on the morning train less the Alexandria Artillery.

Receiving travel orders on May 5, the battalion left by train at 11 p.m. This time they reached only Springfield Station, ten miles away, when they found the orders were a mistake. By noon on the 7th, they were back in Alexandria. This time, Colonel Taylor was questioned by authorities as to his premature evacuation of the city. He reported the withdrawal was due to the inefficient condition of a large part of his battalion and the vulnerability of his exposed and indefensible position. Taylor wrote that the two Irish companies, totaling about 240 privates, were armed with altered flintlocks without cartridges or caps. The Mount Vernon Guard had new muskets, but 52 of the 86 privates were without accouterments, 15 without arms, and very few had much ammunition. The 53 Warren Rifles had minie rifles with nine rounds each while the 85 rank and file of the Old Dominion Rifles had minie rifles with an average of five rounds and four caps each. Although Taylor's report did not include the Alexandria Rifles, another made about the same date reported the 69 men had 50 muskets and no ammunition. The 40 privates of Captain Ball's cavalry company had carbines and sabers but a limited amount of ammunition. Captain Powell's Fairfax Cavalry numbered 30 with only 22 mounts and only a few Colt revolvers.

The authorities in Richmond and Potomac Department headquarters at Culpeper Court House were evidently not satisfied with Taylor's report. He lost his command on May 10. His replacement was Colonel George Hunter Terrett, who had resigned from the U. S. Marine Corps on April 22 and had been commissioned as a colonel in the Provisional Army of Virginia by May 7, 1861. Major Corse had served as assistant general under Taylor and continued in that capacity under the new commander.

The arrival of the gunboat Pawnee at Alexandria caused quite a bit of excitement. Concern arose over the increased possibility of an enemy advance from Washington. Guards were placed at the foot of Cameron Street to keep an eye on the blockading steamer. Those not on guard duty were regularly at drill by squad, by company, and by battalion—occasionally under the command of Colonel Terrett.

On May 18, another Irish company, the O'Connell Guard, was organized under Captain Stephen W. Prestman and composed largely of railroad workers. The Alexandria Gazette of May 23 carried an appeal for ladies to help make uniforms for the new company.

It was also on May 23, 1861 that the polls opened in Alexandria for the purpose of voting on ratification of the ordinance of secession. Only 106 voted in opposition, while 983 ratified the ordinance. By 2 a.m. on the 24th, Union troops had crossed the Potomac River bridges into Virginia. Steamers carrying the 11th New York Fire Zouaves under Col. Elmer E. Ellsworth arrived at the foot of King Street. As the Zouaves landed, pickets fired shots warning of the enemy's approach and began falling back toward the city. At about 3 a.m., Captain Simpson rushed to his Warren Rifles: "Wake up, boys! They are coming! By George, they are across the bridge!"

Lieutenant Reigart B. Lowry, U. S. Navy, left the Pawnee about 4:30 a.m. to meet with Colonel Terrett and demand the surrender of Alexandria. The surrender was refused and Terrett announced he would evacuate the city. He ordered the battalion to assemble at Lyceum Hall and await further orders. Learning of the enemy approach by Washington Street, the battalion was ordered to depart by way of Duke Street at about 6:50 a.m. The Old Dominion Rifles were almost captured at Peyton's Grove when they were late getting the order. Captain Herbert managed to get his riflemen up to the retreating column as it moved westward on Duke Street and avoided their capture. As they evacuated the city, they were told that James Jackson had killed Col. Ellsworth and was, himself, killed instantly by Pvt. Francis Brownell while attempting to retrieve the Confederate flag Ellsworth had removed from the roof of the Marshall House. [The Smithsonian Institution has an excellent on-line exhibit of the Marshall House incident which includes images of Jackson's shotgun, Brownell's percussion rifle, a piece of the captured flag and bloodstained floor cover.] Just west of the Orange and Alexandria Railroad depot, Terrett's command stopped several trains returning from the Springfield Station. The entire command boarded trains and traveled 27 miles to Manassas Junction.