The 4th Maine Volunteer Infantry Regiment was organized in Rockland in May 1861 and was mustered in on June 15, 1861 commanded by Colonel Hiram G. Berry. Four Knox County companies from Searsport, Winterport, Wiscasset, Damariscotta and Belfast were mustered. The regiment was mustered out of service July 19, 1864. The veteran volunteers and recruits were transferred to 19th Maine Infantry. The regiment is noted for their coordinated attack at Gettysburg under Elijah Walker with the 1st U.S. Sharpshooters against General Longstreet's forces, and their part in a severe fight at the Devil’s Den. The regiment was comprised of Company A - Belfast Artillery, Company F - Brooks Light Infantry, and Company K - Belfast City Grays.
Regimental enrollment was 1,440 men. By the time the regiment mustered out, there were 170 killed or dead of wounds, 443 wounded, 137 dead from disease, and 40 in Confederate prisons.
They served in the following engagements:
- First Manassas (First Bull Run) - July 21, 1861
- Yorktown, VA - April 5- May 4, 1862
- Williamsburg, VA - May 4, 1862
- Seven Pines, VA - May 31, 1862
- Gaines Mill, VA - June 27-28, 1862
- White Oak Swamp, VA - June 30, 1862
- Malvern Hill, VA - July 1, 1862
- Second Manassas (Second Bull Run) - August 29-30, 1862
- Chantilly, VA - September 1, 1862
- Fredericksburg, VA - December 13, 1862
- Chancellorsville, VA - May 1-4, 1863
- Wapping Heights, VA - July 21-23, 1863
- Kelly's Ford, VA - November 7, 1863
- Mine Run, VA - November 26-December 1, 1863
- Wilderness, VA - May 5-7, 1864
- Spotsylvania, VA - May 7-20, 1864
- Po River, VA - May 11, 1864
- North Anna, VA - May 23-27, 1864
- Totopotomy, VA - May 26-30, 1864
- Cold Harbor, VA - May 31- June 12, 1864
