His ancestors changed the spelling of their surname "Reynaud" to the more Anglicized "Reno" when they arrived in the United States from France in 1770,[1] landing west of the present city of Richmond, Virginia on the James River.

Reno was admitted to the United States Military Academy in 1842 and graduated eighth in his class of 59 cadets in 1846, initially commissioned a brevet second lieutenant of Ordnance.

[3] During the Mexican–American War in 1847, Reno commanded an artillery battery under General Winfield Scott and fought in the Siege of Vera Cruz and other battles in Mexico.

After the Mexican–American War ended, Reno served in several locations, including as a mathematics instructor at West Point, as the secretary of a group assigned to "create a system of instruction for heavy artillery",[5] and at the Ordnance Board in Washington, D.C.

Upon leaving Alabama with his small force, Reno was temporarily assigned to command the Fort Leavenworth Arsenal until he was appointed brigadier general of volunteers in the fall of 1861.

Elements of Lee's army defended three low-lying "gaps" of South Mountain—Crampton's, Turner's, and Fox's—while concentrating at Sharpsburg, Maryland, to the west, the location of the subsequent Battle of Antietam (September 17, 1862).

In the Battle of South Mountain on September 14, Reno stopped directly in front of his troops as he reconnoitered the enemy's forces advancing up the road at Fox's Gap.

[10] The manuscript of Union Officer Ezra A. Carman, published in The Maryland Campaign of September 1862, Volume 1: South Mountain, Edited and annotated by Thomas G. Clemens, ISBN 978-1-932714-81-4, documents Reno's death by men of General John Bell Hood who were in and fired from the woods that the 35th Massachusetts skirmishers had just retreated from.

Sturgis, a long-time acquaintance and fellow member of the West Point Class of 1846, thought that he sounded so natural that he must be joking and told Reno that he hoped it was not as bad as all that.

On April 9, 1867, his remains were reinterred in Oak Hill Cemetery in Georgetown, Washington, D.C.[13][14] A memorial marking the location of his death was erected in 1889 by IX Corps veterans on present-day Reno Monument Road in Fox's Gap at the South Mountain State Battlefield Park.

Gen. Samuel L. Garland, Jr. of Virginia also killed near here was erected nearby in 1993 by the Sons of Confederate Veterans and the Central Maryland Heritage League along with a large stone and bronze sculpture to North Carolina soldiers defending the line in 2005.