The Civil War prompted the construction of several coastal defense batteries located inside the Golden Gate. Initially these defenses were built as temporary wartime structures rather than permanent fortifications and one of these was constructed in 1864 at Point San Jose, as the location of Upper Fort Mason was then known. A breast-high wall of brick and mounts for six Rodman cannons and six 42-pounder guns were built on the site. Excavation in the early 1980s uncovered the well-preserved remains of the western-half of the temporary battery, and it has now been restored to its condition during the Civil War.