Gaston G. Allen was born on March 30, 1820, in New York. He moved to Cuyahoga County, Ohio, and married Eveline A. Johnson there on January 2, 1848. She died soon afterward, and he married Catherine Friedmann in 1852. He enlisted in the Union army on May 5, 1864, and mustered in as a private in Company G of the 150th Ohio Infantry (National Guard) later that day. He mustered out in Cleveland, Ohio, on August 23, 1864. In 1870, he was working as a ship carpenter in Vermillion, Ohio, and he owned $2,500 of real estate and $200 of personal property. A decade later, he was living in Cleveland, Ohio. He applied for a federal pension in May 1891 and secured one soon afterward. He died in Cleveland on February 20, 1908.