The Third Potomac Home Brigade Infantry, commanded by Col. W. Gilpin, embarked on transports at Annapolis, June 27th, and moved to Baltimore, whence it proceeded next day by rail to Elysville, on the Baltimore and Ohio Railroad. Two important iron bridges, crossing the Patapsco at this point, were threatened with destruction by Stuart's cavalry, then advancing on the right flank of the Army of the Potomac towards Pennsylvania. The preservation of these bridges was of great importance to the government, the Baltimore and Ohio Railroad being the principal route of supply and communication between Washington, Baltimore, and Gen. Meade's army. The service, therefore, rendered by the Third at Elysville and vicinity, although not of a nature involving much personal danger or hardship, like that in the field, was of vast importance, and the most valuable of all the railroad arteries upon which the Union army depended for supplies was successfully guarded at this vital point. The regiment, with detachments posted at different stations from Ellicott's Mills to the Monocacy Junction, remained on railroad guard duty during the ensuing fall and winter and the following spring.
As has already been stated, Vernon and Summer's companies of Cole's cavalry crossed the Potomac from Virginia into Maryland at Harper's Ferry on the 16th of June. Next day White's battalion of Confederate cavalry (mostly Marylanders) made the passage of the river at Point of Rocks and captured a small squad of Mean's Virginia (Union) cavalry. It afterwards intercepted a train of freight-cars, and captured a number of men belonging to Alexander's battery en route from Harper's Ferry to Baltimore. They were all sent South as prisoners of war. Vernon's and Summer's companies, while marching from Harper's Perry to Point of Rocks, for the purpose of guarding the fords of the Potomac, encountered White's command at Catoctin Creek. Mistaking the enemy for friends, both companies were at first surprised and thrown into confusion by his attack, but after the loss of a few men they rallied and drove back the foe, capturing one prisoner. In Capt. Summer's company one man (Joseph L. Michael) was killed, three wounded, and four captured. Capt. Vernon also lost several men taken prisoner. On the 18th of June three of Summer's men, sent with some of Vernon's company on a scout to Frederick, were captured in the town after a lively resistance. Summer's company then went to Berlin, where it remained until the 30th of June, on which date it moved by way of Maryland Heights to Frederick City. At this place it was employed in scouting through the surrounding country and doing patrol duty in the city. Two of its members (couriers) were captured near Emmittsburg on the 5th of July by Stuart's cavalry. Meantime, from the 18th to the 21st of June, Companies A, C, and D of Cole's battalion were kept constantly in motion watching the movements of the Confederate army. The former operated east of the mountains, and the two latter on the west. As a central point from which to direct the movements of his command, Maj. Cole established his headquarters at Burkettsville. On the 22nd, Company A, Capt. Vernon, numbering but thirty men, entered Frederick by the Manor road, and dashing along Market and Patrick Streets, drove out the First Maryland (Confederate) Cavalry Battalion, commanded by Maj. Harry Gilmor. Boldly charging through the streets, Company A, with Lieut. Link leading the advance, pushed the enemy beyond the city limits on the Hagerstown road. Discovering a larger force outside the city preparing to re-enter, Capt. Vernon prudently withdrew his company towards Point of Rocks. One of the Confederates was badly wounded and taken prisoner. He was paroled and left in the hospital. This brilliant dash was executed amid the plaudits of the parents, wives, and friends of many of the men. While the bullets whistled, these patriotic friends waved their handkerchiefs and cheered the men on to victory. Next day the entire battalion, under Maj. Cole, moved on a reconnaissance over South Mountain to Boonsboro'. On the 24th it skirmished with the enemy's column advancing into Pennsylvania, and captured quite a number of prisoners. From this point Company C, Lieut. W. A. Homer, pushed forward on the right flank of the Confederate army, through Wolfsville and Sabillasville, into Pennsylvania, making some effective dashes at the enemy and capturing a number of prisoners, among them a bearer of dispatches from Gen. Lee to Gen. Ewell. At Fountaindale, on the 28th of June, it had a lively skirmish with a small body of the enemy's cavalry, capturing the lieutenant in command, three sergeants, and eight privates, with their arms and equipments and twenty horses. Companies A and D had returned from Boonsboro' to Knoxville, where they were rejoined on the 30th of June by Company C. On the 1st of July these companies established camp at Frederick, where they performed provost duty and operated in different directions as occasion required through the month of July. On the 4th of July a squad of the enemy's cavalry, which dashed into Frederick on the Harper's Ferry road, was driven back and pursued to Knoxville by the battalion. Next day it drove a party of Confederates from Sandy Hook across the bridge at Harper's Ferry and burnt the bridge.
From the time the enemy entered until he withdrew from the State, many of Maj. Cole's command, both officers and men, were detailed as guides, couriers, etc., to the various corps commanders of the Army of the Potomac. In this capacity they rendered most valuable service, their familiarity with the country being thus turned to good account.
After the evacuation of Maryland Heights by the Maryland Brigade, as described at the beginning of the Maryland and Pennsylvania campaign, it proceeded to Frederick City, where it arrived on the afternoon of July 1st. The command bivouacked just outside the city in a clover-field, with the exception of the Seventh Regiment, which, having had the advance on the march, was detailed for picket duty. Next day, July 2nd, the great battle of the war raged at Gettysburg, within hearing of the troops at Frederick, and Gen. French, commanding the Federal forces, fully appreciated the responsibility of his position. On the morning of that day he issued a ringing order, concluding with the announcement that " any officer, no matter how high his rank, or soldier who fails to do his duty at this moment will be made to suffer death under immediate trial before a Drum-Head Court." Gen. French followed this up in a way that showed he meant business. He visited the outposts and camps, found fault with everything, reprimanded everybody, and put under arrest men and officers of all grades. Upon the whole, it had a capital effect.
At night the Seventh was relieved on picket by the Eighth, and the next morning the entire force was paraded through town in column of platoons (equalized), field-music playing, on the march to Monocacy Junction. The brigade never appeared to better advantage.
At the corner of Market and Patrick Streets the column passed Gen. French in review, and at all points was loudly cheered. When Gen. Meade ordered the evacuation of Maryland Heights, he directed Gen. French to march his column rapidly northward and unite with the main army. He was, however, subsequently directed to hold Frederick, camping his troops in the immediate vicinity, to guard the rail and turnpike bridges over the Monocacy. He was further directed to guard the Baltimore and Ohio Railroad from Frederick to a junction with Gen. Schenck, and in the event of the Federal array being compelled to retire before the enemy, to fall back into the defenses of Washington. At Monocacy Junction the brigade guarded the bridges over the Monocacy and the approaches from Nolan's and other ferries of the Potomac, and kept open the line of communication between Washington and Meade's army.
Soon the news of a victory at Gettysburg flew like wildfire. There was, however, no time for a Fourth of July celebration. All was activity and vigilance, constant marching and countermarching, posting of pickets and calling them in again, and hourly expectation of something important to happen. During the afternoon of the 4th the brigade was countermarched back to its old bivouac on Rizer's farm, west of Frederick, on the Harper's Ferry road.
At reveille on the morning of the 6th, when the men paraded for roll-call, they descried an object swinging from the limb of a tree in an adjoining field. It was soon learned that it was the body of an alleged Confederate spy, caught with the evidences in his boots, and hung by order of Gen. John Buford, who commanded a brigade of Union cavalry, which had arrived during the night from Gettysburg. The deceased was recognized as a visitor to the camps of the Maryland Brigade on Maryland and Bolivar Heights, offering various small articles for sale, and getting up ornamented company rolls.
On the afternoon of the 6th of July, Gen. Kenly was ordered to march with the First, Fourth, and Eighth Regiments and Miner's Indiana battery to retake and occupy Maryland Heights. Starting immediately, and making a forced march, Gen. Kenly reached Knoxville