Emilio was born on December 22, 1844 in Salem, Massachusetts, the son of a Spanish immigrant who made his living as a music instructor. Although the minimum age for service in the Union army was 18, in 1861 — at age 16 — Emilio gave his age as 18 and enlisted in Company F of the 23rd Massachusetts Volunteer Infantry. He was noticeably brave and steadfast, and by September, 1862 he had been promoted to the rank of Sergeant.
Emilio was among the group of original officers of the 54th selected by Massachusetts War Governor John Albion Andrew. He mustered in as a 2nd Lieutenant on March 30, 1863. Two weeks later, he was promoted to 1st Lieutenant, and on May 27, he was made Captain of Company E. Captain Emilio emerged from the ferocious assault on Fort Wagner on July 18, 1863 as the regiment's acting commander, since all of the other ranking officers had been killed or wounded. He fought with the 54th for over three years of dangerous combat, mustering out of the Union army on March 29, 1865, still not yet 21 years old.
Following the war, he went into the real estate business, first in San Francisco, and later in New York. After assisting two old comrades documenting the history of the 23rd Massachusetts regiment in the mid-1880s, he began work on his own documentation of the 54th, publishing the first edition of Brave Black Regiment in 1891, and the revised edition in 1894. He died in New York on September 16, 1918 after a long illness, and was buried in Salem, Massachusetts.
- Captain Luis F. Emilio, A Brave Black Regiment. The History of the 54th Massachusetts, 1863-1865, New Introduction by J.W. Urwin. Da Capo Press, Cambridge, MA, 1995; paperback, 452 pages. ISBN 0306806231; ISBN 978-0306806230. Reprint (with a new introduction) of the second enlarged edition, originally published in 1894, Boston. First edition published 1891.