Battery Mendell was the first of the batteries built at Fort Barry. Construction was started in July 1901 and was completed in 1902.
On 22 November 1902, War Department General Order 120 named the battery after Colonel George H. Mendell, Corps of Engineers. After his graduation from the United States Military Academy in 1852, Colonel Mendell began a long career in planning and designing military structures. During the late 19th century he had supervised a majority of the post-Civil War and early Endicott-type fortifications that protected San Francisco Bay. In 1902 Colonel Mendell died in San Francisco.
In 1905, two M1895A4 12-inch breech loading rifles (numbers 4 and 6) made by the Bethlehem Steel Company arrived on site. They were mounted on disappearing carriages (Model 1897, numbers 30 and 31) fabricated by the Midvale Steel Company. These guns fired a 1,100 pound projectile over eight miles.
These guns remained emplaced until 1943, when the threat of imminent invasion was over and more modern Battery Elmer J. Wallace was reactivated following that battery being casemated. The guns were removed and scrapped that same year.
For decades, the battery fell into disrepair and was a target for vandals. But today, thanks to the National Park Service, portions of the battery are being repaired and restored.