Campbell Allen was born on February 8, 1830, in Nelson, New York. By the early 1860s, he was working as a school principal in Albany, New York. He married a woman named Amanda, and they had at least three children: Sophie, born around 1859; Arthur, born around 1861; and Jessie, born around 1865.
In September 1861, he received a commission as a captain in Company F of the 44th New York Infantry. The regiment took part in the Peninsula campaign, the Seven Days’ Battles, the Second Battle of Manassas, the Battle of Antietam, the Battle of Fredericksburg, the Battle of Chancellorsville, the Battle of Gettysburg, the Overland Campaign, and the siege of Petersburg. He was promoted to major on August 27, 1863, and he mustered out on October 11, 1864.
He returned to Albany after leaving the army, and he became a police superintendent in 1865. He later worked in the insurance industry. He supported the Republican Party, and a local writer declared him a “man of marked ability, both natural and acquired.” He died suddenly in Albany on October 6, 1877.