This Regiment was organized at Portland, Me., August. 29th, 1862, to serve three years. Left Sept. 3d for Boston, whence they sailed in the steamer Merrimac for Alexandria, Va., Arriving on the 6th, and proceeding the next day to Washington, where they went into camp near the Arsenal Grounds. In a few days they marched rapidly towards the field of active operations in Maryland until they reached the battlefield of Antietam, and were drawn up in line of battle, but not ordered forward, being a portion of Butterfield's Brigade, of Porter's Division, which was held in reserve. They afterwards encamped near Antietam Ford.

At the battle of Fredericksburg, on the 13th of December, they were under fire for the first time, and rendered conspicuous service, being under the hottest fire for thirty-six hours, after which they were withdrawn to the city, where they bivouacked a few hours, then recrossed the river and encamped near Falmouth, where they remained until the battle of Chancellorsville in May, 1863.

During the battle of Chancellorsville they were detached to guard the telegraph line, and although exposed to artillery fire, suffered no loss.

On the 20th of May they joined in the movement towards Pennsylvania, engaged the enemy near Middleborough, Va, on the 21st of June, and after a sharp fight drove them to Upperville, losing in trhe engagement 1 man killed and 8 wounded.

They arrived on the battle-field of Gettysburg on the 2d of July, and on that day were hotly engaged with the enemy, losing 3 commissioned officers killed and 134 enlisted men killed and wounded. On the 3d they were under heavy fire of artillery, but took no active part, and on the 5th joined in the pursuit of the enemy; participated in a skirmish on the Sharpsburg Pike on the 10th, and took part in the affair at Wapping Heights on the 23rd.

Returning from Manassas Gap, they encamped at Warrenton and Beverly Ford until the 16th of September, when they moved beyond Culpepper.

On the 10th of October they participated in the movement to the Rapidan, retreating the next day through Culpepper, across the Rappahannock River, and supported the 2d Corps in the engagement at Bristow Station on the 13th.

On the 7th of November they took part in they assault and capture of the enemy's works at Rappahannock Station, losing 1 man killed and 7 wounded, and afterwards moved across the river at Kelley's Ford.

On the 28th they joined in the movement to the Rapidan, where they were in position before the enemy's works until Dec. 3d, when they formed the rear guard of their corps on the retreat from that place, and on the next day went into camp near Rappahannock Station, Va. They remained in winter quarters at Rappahannock Station until May 1st, 1864.

On the 4th of May they crossed the Rapidan at Germania Ford, and on the following day were hotly engaged with the enemy on the left of Locust Grove Road, with a loss of 1 officer and 10 men kiilled, 58 men wounded and 16 missing.

On the 6th of May they remained in line of battle in front of the works, losing 2 men killed and 10 wounded. On the 7th they advanced upon the enemy's line to ascertain his position and force, and were withdrawn after a loss of two officers killed and 1 wounded, and 2 enlisted men killed and 10 wounded.

On the 8th they proceeded to Spoittsylvania Court House, and formed in line of battle at Laurel Hill. They were then ordered to report to Gen. Crawfort, commanding 2d Division, 5th Corps, advanced towards the enemy, and lay under a heavy fire until 6 P. M., when they assisted in repelling the enemy's charge, losing 1 officer and 5 men killed, 2 officers and 13 men wounded, and 2 men missing.

From the 13th to the 20th they occupied rifle pits in front of the enemy from Spottsylvania, and lost 4 men killed.

On the 23rd they crossed the North Anna River, and participated in the action at that place; thence pushed on to the Virginia Central Railroad, a part of which they destroyed.

On the 30th they advanced towards Hanover Court House, skirmishing with the enemy, and forcing him back during the entire day.

Fighting being renewed on the 3d of June, they again engaged the enemy and assisted in compelling them to fall back to the rear of a swamp to a second line of works, losing 2 enlisted men killed, 1 officer and 23 men wounded, and 1 missing.

On the 13th they crossed the Chickahominy, and arrived in front of Petersburg on the 18th, where they remained entrenched and under fire until Aug. 15th, when they were withdrawn, and on the 18th assisted in the capture of the Weldon Railroad. They remained on the Weldon Railroad until Sept. 30th, when they moved with their division and charged the enemy's works at Preble's Farm, across an open field, under a terrible fire of musketry and cannister. They afterwards assisted in checking the enemy's advance, and held their ground. Their loss in these actions was 1 officer and 6 men killed and 50 men wounded.

On the 2d of October they moved to the front and threw up earthworks, where they remained until Oct. 17th, when they took part in a reconnoissance to Hatcher's Run, losing 1 man killed and 2 wounded.

Afterwards returned to their former position and remained building forts, strengthening works, &c., until Dec. 6th.

On the 7th they joined the expedition to the Weldon Railroad, which they struck at a point between Stony Creek and Jarrett's Depot, and assisted in the destruction of about twenty miles of this road; then returned and went into camp near the Jerusalem Plank Road, where they remained until Feb. 5th, 1865, when they moved to Hatcher's Run and took part in the action at that place on the 6th, with but slight loss.

They remained in camp at that place until the 27th of March, when they moved across the Run and supported Gen. Chamberlain's Brigade in the action on the Quaker Road.

The following day skirmished with the enemy and gained possession of the Boydton Road,

On the 31st they were engaged in the action at Gravelly Run, and on the 1st of April at Five Forks. At the latter place they were one of the first to gain the works of the enemy, where they captured one battle flag and a large number of prisoners. They afterwards joinedin the pursuit of the enemy and came up with them on the 8th at Appomattox Court House.

At the time of the surrender of the rebel army the regiment was skirmishing with the enemy, and at the completion of the terms of surrender, was one of the regiments designated to receive the rebel arms.

On the 15th they proceeded towards Washingtobn, where they arrived on the 12th of May.

On the 5th of June the enlisted men whose term of service expired prior to Oct. 1st, 1865, were mustered out and most of the officers discharged. Subsequently the men remaining of the 16th Me. Volunteers and the 1st Regiment of Sharpshooters, were consolidated with the 20th, and the regiment thus reorganized remained in service until July 16th, 1865, when it was mustered out of the U. S. service near Washington, D. C., by Capt. Charles F. Sawyer, Assistant Commissary of Musters, 3d Division, Provisional Corps, in accordance with orders from the War Department.

They arrived at Portland, Me., on the 20th, where the men were paid and finally discharged on the 15th.