While not much information could be found regarding the birth, death, or any possible marriages of Henry P. Adams, it is known that he resided in Franklin, Massachusetts at some point in his life. During the Civil War, he served in both the 13th Regiment Massachusetts Volunteer Infantry and the 1st Battalion Massachusetts Heavy Artillery. While in the 13th Regiment, he was placed in Company H and while in the 1st Battalion, he was in Company C. Both stations he was in took part in significant battles.

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            The 13th Regiment Massachusetts Volunteer Infantry was assembled in 1861. They were first sent to Maryland. By the late summer and into the fall of that year, the Regiment placed guards on the upper part of the Potomac River between Hagerstown and Darnestown, Maryland. The following year, 1862, the regiment proceeded to cross the Potomac River.

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            Later in 1862, the 13th Regiment fought in the Second Battle of Bull Run under the command of General Hartsuff. During this battle, they were engaged at the Thoroughfare Gap where, on August 28, 1862, they resisted the advancing troops of General Longstreet. Then, on August 30, General Hartsuff fell ill and so General Z.B. Tower took over command. Under their new general, the 13th Regiment became engaged near Bald Hill where they lost thirty-six officers and several other men were either killed or mortally wounded. Because of this, the 13th Regiment was the combined with the 12th.

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            On September 17, 1862, the 13th Regiment was engaged in the Battle of Antietam. This battle was won by the Union Army, but the victory came at a high cost. Antietam was the bloodiest single day battle during the Civil War. At least 48,000 men were wounded on both sides - 21,000 on the Union side and 27,000 on the Confederate side. After the battle, the 13th Regiment spent the winter of 1862 in a camp near Fletcher’s Chapel which is near Belle Plain.

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            From May 1 to May 4, 1863, the 13th Regiment fought in the Battle of Chancellorsville under the command of General Robinson and General Leonard. The Confederates prevailed in this battle, but it was a fight to the finish. Because Stoneman’s Cavalry was missing in action, the Union Army was deprived of much needed intelligence on the strength of the Confederate Army. It is thought that if the cavalry had been there, General Hooker may have won the battle. While the 13th Regiment's losses in this battle were minimal, the Union Army as a whole lost about 18,000 men. The Confederate Army lost about 13,000.

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            On July 1, 1863, the 13th Regiment became engaged in the Battle of Gettysburg under the command of General Robinson. They were posted on the right of the troops near Oak Hill and lost many men. Once the battle had ended, Confederate General Robert E. Lee gave up all hope of trying to invade the North, and most people consider this the turning point of the Civil War. At least thirty percent of all of the soldiers involved in the battle were dead by the end of it. The Union army suffered a loss of 23,000 men and the Confederate Army suffered a loss of 28,000.

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            The Battle of Gettysburg was the last major battle for the 13th Regiment. On July 14, 1864, the 13th Regiment’s active duty ended. The re-enlisted men were sent to the 39th Regiment, which was not the case Henry P. Adams. Instead, Adams joined the 1st Battalion Massachusetts Heavy Artillery which organized in April of 1865 with Companies A through F. Adams was placed in Company C and placed on duty at Fort Warren in Massachusetts under Colonel Justin Dimmick. The fort served as a training center for several regiments and was also a detention site for prisoners of war. Company C stayed at Fort Warren until October 20, 1865.