The 4th United States Infantry Regiment lost 2 officers and 58 enlisted men killed or mortally wounded and 1 officer and 61 enlisted men to disease during the Civil War. It is referenced by War Department markers at Antietam and honored by a monument at Gettysburg.

1861
January Stationed at ten different posts on the Pacific slope from Puget Sound to the Gulf of California. Ordered to concentrate at Camp Sumner, San Francisco for movement to Washington, D.C. and duty in the Defenses of that city. Five junior officers resigned to enter Confederate service.
September 9 Major Robert C. Buchanan was promoted to lieutenant colonel.
November 27 Defenses of Washington DC, commanded by Lieutenant Colonel Buchanan.
1862
March Attached to Sykes’ Regular Infantry (Reserve) Brigade, Army of the Potomac and moved to Virginia Peninsula
April 5-May 4 Siege of Yorktown, Virginia
May 24 Attached to 1st Brigade, 2nd Division, 5th Army Corps, Army of the Potomac. Lieutenant Colonel Buchanan took command of the brigade as senior officer.
June 25-July 1 Seven Days before Richmond.
June 26 Battle of Mechanicsville
June 27 Gaines’ Mill
June 29
Savage Station

The train conveying the regimental records, baggage and supplies, was burned to prevent its falling into the hands of the enemy. For nearly a week, officers and men had to eat and shelter themselves whatever they could forage.

June 30
Turkey Bridge (Battle of Glendale)

The regiment was the last to cross the already partly destroyed “Grapevine Bridge.”

July 1
Malvern Hill
July At Harrison’s Landing
August 16-28 Movement to Fortress Monroe, then to Centerville
August 28-September 2 Pope’s Campaign in Northern Virginia
August 29 Battle of Groveton
August 30
Second Battle of Bull Run
September 6-22 Maryland Campaign
September 16-17
Battle of Antietam

Eight companies of the 4th United States Infantry were at the Battle of Antietam, commanded by Captain Hiram Dryer.

From the War Department marker on the Antietam battlefield:

On the morning of the 16th, the 4th Infantry seized the Middle Bridge over the Antietam: Companies B, G, I and K were thrown across the bridge, deployed on either side of the road, advanced about 300 yards, and, between 2 and 4 P.M., became engaged with the enemy’s skirmishers. They were relieved at sunset by the I st Battalion, 12th U.S. Infantry and recrossed the Antietam. Between 2 and 3 P.M. of the 17th, the Regiment again crossed the Antietam, under orders to support the Horse Batteries. It advanced beyond the Batteries and took position in the field to the right, the left resting on the road at this point. Companies G, I and K, under Lieut. C. H. Carlton, were deployed as skirmishers and, advancing in a westerly direction, encountered the Confederate skirmishers posted behind a rail fence. The skirmishers suffered severely from an enfilading fire of canister from Cemetery Hill, south of the turnpike, and from the enemy’s skirmishers in their front.

At about sunset the skirmishers were withdrawn and the regiment, carrying its dead and wounded, recrossed the Antietam.

September 19-20 Shepherdstown Ford
October At Sharpsburg
October 16-17 Kearneysville and Shepherdstown
October 29-November 19 Movement to Falmouth, Va.
December 12-15 Battle of Fredericksburg
1863
January 20-24 “Mud March”
April 27-May 6 Chancellorsville Campaign
May 1-5
Battle of Chancellorsville
June 11-July 24 Gettysburg Campaign
July 1-3
Battle of Gettysburg

Only four companies with 173 enlisted men were present

From the monument on Houck’s Ridge at Gettysburg:

Four Companies.
Captain Julius W. Adams, Jr. commanding

July 2 Arrived in the morning and took position near the line of the Twelfth Corps. The Regiment with the Brigade moved from the right to the left of the line and at 5 p.m. advanced across Plum Run near Little Round Top and supported the Second Brigade in its advance to the crest of the rocky wooded hill beyond and facing to the left engaged the Confederates but returned under a heavy fire on both flanks and from the rear after the Confederates had gained a position in the Wheatfield in the rear of the Brigade.

July 3 Remained in the same position.

July 4 The Regiment with the Brigade made a reconnaissance and developed a force of the Confederate Infantry and Artillery in front and engaged on the skirmish line well to the front.

Casualties: killed 10 men, wounded 2 officers and 23 men.

July 5-24 Pursuit of Lee
August 15 Moved to New York and attached to Dept. of the East for duty supression draft riots. Stationed for three weeks in Washington Square.
September Moved to Forts Tompkins and Wood
1864
April 25 ReJoined Army Potomac, attached to 1st Brigade, 1st Division, 9th Army Corps
May 4-June 12 Rapidan Campaign
May 5-7
Battle of the Wilderness
May 8-21
Spotsylvania Court House
May 10 Ny River
May 22-26 North Anna River
May 26-28 On line of the Pamunkey
May 28-31 Totopotomoy
June Attached to 1st Brigade, 2nd Division, 5th Army Corps
June 1-12
Cold Harbor
June 1-3 Bethesda Church
June 16-18 Before Petersburg
June 22 Ordered to City Point, Va. and assigned to Headquarters, Army Potomac, numbering only 134 men fit for duty
1865
April 2 Fall of Petersburg
May Provost Duty at Richmond, Va. attached to Dept. of Virginia
July 15 Moved to N.Y. Harbor. A detachment with a number of officers was sent to West Point conveying the colors of the regiment, including some that had been carried in the Mexican War. The Corps of Cadets was paraded and joined the escort of the tattered and shot ripped flags to the Post Chapel where they were finally deposited.