Organized at Augusta, Me., in March and April, 1 864. Leaving the State, April 18th, it proceeded to Alexandria, Va., where it was assigned to the 2nd Brigade (General S. G. Griffin's), 5d Division (General R. B. Potter's), Ninth Corps. In less than a month after leaving home the regiment went into action at the Wilder ness, and on May 12th was hotly engaged at Spotsylvania, where it lost 11 killed, 94 wounded, and 1 missing. In the fighting at Bethesda Church, June 3d, it lost 15 killed and 39 wounded, and behaved with such gallantry that General Griffin complimented it in orders. Under command of Colonel White, the regiment rendered efficient service in the assault on Petersburg, June 17th, and at the Mine explosion it was among the first to enter the enemy's works. Its losses at the Mine were 9 killed, 56 wounded, and 51 captured or missing. In October there were only about 60 men left on duty; then two new companies joined the regiment, which were designated as L and M, and in December the regiment received an accession by the consolidation with it of the Thirty second Maine; 485 men were thus transferred on the rolls, of whom only 181 were present for duty. In less than one year's time the Thirty-first Maine lost 674 men, killed or wounded in action, three-fourths of this loss occurring in May, June and July, 1 864. After the war had ended the regiment was transferred to the Nineteenth Corps, and stationed at Savannah, Ga., until August 20th, 1865, when it was mustered out.