Charles Paine Horton was born in October 1836 in Boston, Massachusetts, to Henry K. Horton and Helen M. Barnes. His father was a merchant who owned $100,000 of personal property by 1860. He grew up and attended school in Boston, and he graduated from Harvard University in 1857. By 1860, he was working as a merchant.
On May 25, 1861, he received a commission as a 2nd lieutenant in Company K of the 2nd Massachusetts Infantry. He was promoted to 1st lieutenant on November 1, 1861, and then to captain in the summer of 1862. He served as assistant adjutant general, and he took part in the Battle of Cedar Mountain, the Battle of Antietam, and the Battle of Gettysburg. He mustered out on September 6, 1865.
Horton returned to Massachusetts after the war, and he reportedly “engaged in business, in which he prospered.” He married Flora Arlin around 1879, but they separated several years later. By 1900, he was living in Bourne, Massachusetts. He died of cirrhosis of the liver in Boston on December 2, 1906.