Charles Pomeroy Stone (September 30, 1824 – January 24, 1887) was a career United States Army officer, civil engineer, and surveyor.

Stone was reportedly the first volunteer to enter the Union Army, and during the war he served as a general officer, noted for his involvement at the Battle of Ball's Bluff in October 1861.

His time at the academy was shared with a number of other recruits who would go on to have important roles in the Civil War and the lead-up to it, including such ardent secessionists as William Logan Crittenden.

Stone stayed at West Point, serving as an assistant professor and teaching geography, history, and also ethics from August 28, 1845, to January 13, 1846.

Stone then fought notably during the Battle of Molino del Rey on September 8, and was appointed a brevet first lieutenant from that date for "gallant and meritorious conduct" in this fight.

[2] He then fought in the Battle for Mexico City until September 15, and was part of a successful climbing party of the volcano at Popocatepetl, raising an American Flag at its summit.

After the war with Mexico ended, Stone returned to the Watervliet Arsenal in 1848, again taking up his position as Assistant Ordnance Officer.

After a dinner with his former commander Winfield Scott, Stone was requested to be Inspector General of the District of Columbia Militia at the rank of colonel as of January 1, 1861, and was thus reputed to be the first volunteer officer mustered into the Union Army before the Civil War.

[8] One of his most important acts in this role was to frustrate an attempt by southern militias and the secret society known as the Knights of the Golden Circle to carry out a coup against the nascent Lincoln administration.

Stone received word that militia groups from Baltimore and surrounding areas intended to infiltrate Washington, D.C., and seize the city by force during Lincoln's inauguration.

[2] In his efforts to carry out his orders and maintain discipline, Stone drew the attention and wrath of his home state's governor, John A. Andrew, and Charles Sumner, the senior U.S. senator from Massachusetts, both powerful and influential Radical Republican politicians.

In late September Stone issued general orders that required his men "not to incite and encourage insubordination among the coloured servants in the neighbourhood".

However, many of the 20th Massachusetts were abolitionists, who disagreed with Stone's insistence on returning runaways back into slavery and wrote both their families and their representatives about the incident.

[12] On October 20, 1861, Stone was ordered by Maj. Gen. George B. McClellan to conduct a reconnaissance across the Potomac River to report on Confederate activities in Leesburg, Virginia.

[13] This message from McClellan's staff related the situation and outlined Stone's orders: General McCall occupied Dranesville yesterday, and is still there.

[14] Stone's division numbered about 10,000 men and was posted around Poolesville, Maryland, about eight miles from Leesburg, with portions of his command at points along the Potomac shore.

He moved his artillery to Edward's Ferry along the Potomac, from which he could shell the woods on the opposite side of the river, held by Confederate forces.

While he led part of his command directly across at Edwards Ferry at 5 p.m., Stone ordered Col. Charles Devens and 300 men of his 15th Massachusetts to immediately cross over to Ball's Bluff that night.

Stone's instructions were to "March silently under cover of night to the position of the camp [and] attack and destroy it at daybreak… and return rapidly to the island".

Devens found no camp since an earlier patrol apparently confused corn shocks as tents in the evening shadows; he halted and asked Stone for instructions, who responded to push closer to Leesburg.

Three of his regiments were ordered to deal with Stone by blocking the road from Edwards Ferry to Leesburg, while the remainder fought and defeated Baker's force at Ball's Bluff.

He then moved toward Harrison's Island, learned of the defeat at Ball's Bluff, and quickly asked McClellan for help from McCall, whom he thought nearby but was actually more than twenty miles away.

[20] Stone bore the brunt of much public criticism; the U.S. Congress Joint Committee on the Conduct of the War was established in the wake of Baker's congressional eulogies and anger over the defeat.

Upon reaching the facility he was put immediately into solitary confinement, but he managed to hire an attorney and waited for official charges to be filed.

He sent several inquiries to McClellan, to the army's adjutant general's office, and to Stanton himself, who stated " …the charges were being reviewed prior to being publicized…", but received no satisfactory explanation.

[26] To hold one commander in prison untried is less harmful in times of great national distress than to withdraw several good officers from active battlefields to give him a trial.

When Maj. Gen Joseph Hooker took over command of the Army of the Potomac in early 1863, he asked for Stone as his chief of staff, but Stanton denied this request as well.

[31] With the facts now known, The New York Times newspaper editorialized: General Stone has sustained a most flagrant wrong—a wrong which will probably stand as the very worst blot on the National side in the history of the war.

[32]Without assignment until May, Stone was ordered to the Department of the Gulf, serving as a member of the surrender commission at Port Hudson and in the Red River Campaign as Maj. Gen. Nathaniel P. Banks's chief of staff.

However, on April 4, 1864, Stanton ordered Stone mustered out of his volunteer commission as a brigadier general and he reverted to his rank of colonel within the regular army.