[1]: 44 [2][3] His father Henry was born in Middlebury, Vermont, on December 12, 1805, and worked as a merchant and banker for most of his life, including as a cashier at the Caledonia National Bank in Danville.

Samuel Mattocks, Charles's grandfather, was the former Vermont State Treasurer, and commanded a Connecticut company during the American Revolutionary War.

During his school years, he was a member of both the Peucinian Society and Delta Kappa Epsilon,[6] and studied elocution and German under professor Joshua Chamberlain.

In May of that year, at the beginning of the American Civil War, Mattocks formed a military company under the name of the "Bowdoin Guards."

"[8] Chaimberlain and Mattocks both enlisted in the Union Army in the summer of 1862, along with 25 other students, three of whom joined Charles in the 17th Maine Volunteers.

[3] A few days after the battle, he and his company were mentioned by name in the official report written by Brigadier General J. H. Hobart Ward, commending "their valuable assistance and gallant conduct on the night of the 2d of May.

Less than a week after Mattocks returned from leave in late March 1864, he was moved from the 17th Maine Infantry and placed in command of the 1st United States Sharpshooters.

[c] On their way back to Union territory, they trekked for two days without food before encountering a slave, who fed them "chicken, corn bread & potatoes.

[3] Mattocks was recaptured 1.5 miles (2.4 km) from the Union lines, on November 28, by Cherokee scouts, then in service of the Confederacy.

Rather than resuming his previous command of the 1st United States Sharpshooters, Mattocks was granted permission from the Secretary of War to rejoin the 17th Maine Infantry Regiment as major.

[5] After the fall of Petersburg, Mattocks led the regiment in the Appomattox Campaign and was distinguished in leading a charge at the Battle of Sailor's Creek.

[1]: 45  Three days later, on April 9, 1865, Confederate General Robert E. Lee surrendered the Army of Northern Virginia at Appomattox Court House.

His regiment of 220 men captured two stands of colors, two pieces of artillery, about 300 prisoners, and a loaded wagon train.

[14] The President of the United States of America, in the name of Congress, takes pleasure in presenting the Medal of Honor to Major Charles Porter Mattocks, United States Army, for extraordinary heroism on 6 April 1865, while serving with 17th Maine Infantry, in action at Deatonsville (Sailor's Creek), Virginia.

Major Mattocks displayed extraordinary gallantry in leading a charge of his regiment which resulted in the capture of a large number of prisoners and a stand of colors.

[4]: 150 Mattocks was an active member of the executive committee of the Union Soldiers and Sailors, a post-war veterans group campaigning against the Democratic Party.

It was described by Campbell's Illustrated Weekly as "one of peculiar shape, being somewhat irregular and running to a point" and designed to be different from any other State's building.