When the forces of the Confederacy fired on the United States flag at Fort Sumter in Charleston Harbor in 1861, the total number of men enlisted in the United States Army numbered about 16,000. During the entire period of the War of Attempted Secession, while the Union Army would number about 2,000,000 men, the total number of men to serve in the United States Army would never exceed 45,000. In other words, only about two percent of the men who wore Union Blue served in the professional Army.

Of the total number of 745 line officers of the United States Army in 1860(another 358 were staff officers), 212 were assigned to the Artillery. Most of these officers were career men from West Point or similar background, as the Army had seen the need for trained officers in the Artillery since 1828. When the regiments were expanded, it was specifically determined that the new Battery Commanders would be promoted from the line and not come from civilian life.

On the eve of the Civil War, the 3rd Artillery was spread wide, with nine companies on the Pacific Coast, two at Fort Monroe, and one in the Department of the West. Headquarters of the 3rd was established at San Francisco, and two companies of the regiment were now developed as light artillery, Company C and Company E, now called the White Horse Battery.

Company G of the 3rd was now moved to two points out in San Francisco Bay, establishing a garrison post on the west side of Angel Island with a small contingent, and also moving with a larger force to a forbidding island with a grim stone-walled work: Alcatraz. Here the 3rd Artillery was placed with duties not only to protect the entrance to the Bay, but to aid in the development of a military prison. This assignment fell to just sixty eight enlisted men, two officers, and fifty two civilians.Command of the 3rd US Artillery at San Francisco was given to Col. Charles Merchant. From the headquarters, Col Merchant was responsible for companies of Artillery stretching from Washington in the north to San Diego in the south.

Not all of the 3rd Artillery's staff were on duty with the regiment. Captain John F. Reynolds had been assigned in 1855 as Commandant of Cadets at West Point, and three other officers were said to be on leave during the pre-war period. By the time the Confederacy fired on Ft. Sumter, the members of Batteries Land M were under strength and under funded as a result largely of actions taken by Congress. In October 1861 these two batteries were combined and ordered East to join theArmy of the Potomac under the command of Gen. George B. McClellan. Upon arrival in the East, the combined Battery L&M was placed under the command of Captain J.N.O. Edwards, a West Point graduate (Class of 1851) as part of Sykes' Division.

When the battery left San Francisco, it had also left its guns. Re-armed in the East with six matched 10-pounder Parrott Rifles, Edwards Battery was sent on McClellan's Peninsular Campaign, serving as the advanced guns in actions such as at Gaines' Mill, where two guns were overrun, and at Malvern Hill a rebel brigade closed to pistol shot range before being driven off.

After the Seven Days' campaign, Edwards' Battery was reassigned to the IX Corps of the Army of the Potomac. Once again the battery was called into action at the Battle of Antietam where it was cited for meritorious service.

Near the end of Spring, 1863, the battery went with the IX Corps to join in the siege of Vicksburg, Mississippi in the Western operations, arriving 6 weeks before the fall of that city in July, 1863. The unit did participate in the siege of Jackson, Mississippi , the siege of knoxville and several other battles in the west before being returned to service in the Army of the Potomac in May 1864, where it served in the Battle of the Wilderness.

While other batteries of the 3rd U.S. Artillery served in the eastern theatre of operations during the Civil War, most were compelled to return to San Francisco to recruit and fill their ranks. However, Battery L&M managed to maintain themselves inthe field throughout the War to Restore the Union.

Summary of 3rd US Battery L&M Service

At San Francisco, Cal., until October, 1861. Ordered to New York October 14, thence to Washington, D.C. Battery L&M combined," Artillery Reserve, Army of the Potomac, March to May, 1862. Artillery, 2ndDivision, 5th Army Corps, Army of the Potomac, to December, 1862. Artillery, 1st Division, 9th Army Corps, Army of the Potomac, to April, 1863, and Dept. of the Ohio to June, 1863. Artillery Reserve, 9th Army Corps, Army of the Tennessee, to August, 1863. Artillery, 1st Division, 9th Army Corps, Dept. of the Ohio, to October, 1863. Artillery, 2nd Division, 9th Army Corps, to January, 1864. Artillery, 1st Division, 9th Army Corps, to April, 1864. Reserve Artillery, 9th Army Corps, Army of the Potomac, to June, 1864. Camp Barry, Defenses of Washington, D. C, 22nd Army Corps, to February, 1865. District of Alexandria, 22nd Army Corps, to August, 1865.

SERVICE.--Siege of Yorktown, Va., April 5-May 4. New Bridge June 19. Seven days before Richmond June 25-July 1. Mechanicsville June 26. Gaines' Mill June 27. Turkey Bridge June 30. Malvern Hill July 1. At Harrison's Landing until August 16. Movement to Fortress Monroe, thence to Alexandria August 16-23. Maryland Campaign September 6-22. Battle of Antietam September 16-17. At Sharpsburg until October 30. Movement to Falmouth, Va., October 30-November 19. Battle of Fredericksburg, Va., December 12-15. "Mud March" January 20-24, 1863. Moved to Newport News February 7, thence to Kentucky March 21-28. Duty in District of Central Kentucky until June. Moved to Vicksburg, Miss., June 4-14. Siege of Vicksburg June 14-July 4. Advance on Jackson, Miss., July 4-10. Siege of Jackson July 10-17. Moved to Covington, thence to Crab Orchard, Ky., August 4-18. Moved to Knoxville, Tenn., September 10-26. Action at Philadelphia October 16. Knoxville Campaign November 4-December 23. Campbell's Station November 16. Siege of Knoxville November 17-December 5. Blain's Cross Roads December 17. Strawberry Plains January 21-22, 1864. Duty in East Tennessee until March. Moved to Annapolis, Md. Rapidan Campaign May 4-16. Battle of the Wilderness May 5-7. Spotsylvania Court House May 8-16. Ordered to Washington, D.C., May 16, and duty in the Defenses of that city and Alexandria, Va., until August, 1865.

3rd Regiment Artillery lost during the civil war 2 Officers and 39 Enlisted men killed and mortally wounded and 3 Officers and 67 Enlisted men by disease. Total 111.