[2] He joined the Union Army as a teenager and served under Generals William Tecumseh Sherman, Nathaniel Lyon and Ulysses S. Grant.

[3] The President of the United States of America, in the name of Congress, takes pleasure in presenting the Medal of Honor to Private Fitz W. Guerin, United States Army, for extraordinary heroism on April 28 & 29, 1863, while serving with Battery A, 1st Missouri Light Artillery, in action at Grand Gulf, Mississippi.

He found better pay stringing telegraph wire for a railroad, but returned to photography, going into partnership and setting up Remington, Guerin, and Mills Gallery in Ottumwa, Iowa.

[6] He was buried at Bellefontaine Cemetery in St. Louis, the same resting place as his Medal of Honor co-recipients, Hammel and Pesch.

A 1982 American Heritage magazine article labeled him a "turbid Victorian hack", though it did concede he was technically gifted.