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[During the Third System] some of the most spectacular harbor defense structures to come out of any era of military architecture were to be found. Included by virtue of their role in the Civil War were certainly some of the most famous--Sumter, Pulaski, Monroe, Pickens, Morgan and Jackson. From the technical standpoint, this large group of massive, vertical-walled forts represented the general embodiment and the fullest development of features which had previously appeared in only a few and isolated instances, i.e., structural durability, a high concentration of armament, and enormous overall firepower. -Emanuel Raymond Lewis, Sea Coast Fortifications Pre-Civil War In March of 1847, U.S. troops occupied the Presidio of San Francisco, and the government of the United States acquired all of the public lands formerly claimed by Mexico. In addition to the Presidio, the U.S. took possession of several islands including Angel and Alcatraz. During this period, the bulk of the current Presidio was acquired. In 1848, the discovery of gold in California gave a new importance to the harbor of San Francisco. Increased trade prompted the military to begin the construction of coastal defenses for the San Francisco Bay.1 In the fortification strategy commonly referred to as the Plan of 1850, cannons mounted at the north and south shores of the Golden Gate would use crossfire on enemy ships entering the bay. In addition, the Plan sought to establish an ancillary fortification inside the bay on Alcatraz Island. With all three of these fortifications in place, hostile ships attempting to penetrate the bay would become trapped in a deadly triangle of fire from all three forts. Construction of these coastal defenses began in 1853.1 Designed to be the equal of any fort in the country, the brick-and-mortar Fort Point, located at the south shore of the Golden Gate, boasted three casemated tiers and a top barbette tier. When construction was completed in 1861, the fort and its outworks had emplacements for 141 guns of various types, but only 55 cannons and 11 mortars were mounted at that time.1 Work went more quickly on the stone-and-brick batteries ringing Alcatraz Island. In 1855, the fortress at Alcatraz was armed with seven 8-inch and one 10-inch Rodman cannon, which were the first permanent American guns placed on the Pacific Coast. Work on fortifications at Lime Point did not begin until 1868 and was suspended soon after initial excavation began.1 Civil War Period With the onset of the Civil War, budgetary purse-strings were loosened, resulting in increased armament on Alcatraz and the placement of fifty-nine cannons at Fort Point Rather than out of immediate concern for Confederate naval action, the increased military budget for the San Francisco Bay was a reaction to British reinforcement of Vancouver Island, which ignited fears that British forces might attempt to seize California while the United States was preoccupied with the Civil War in the east.1 
Photo courtesy of the National Archives and Records Administration The Civil War also prompted the construction of an inner-line of batteries first proposed in the Plan of 1850, which were to be located inside the Golden Gate. However, unlike Fort Point, these defenses were built as temporary wartime structures rather than permanent fortifications. On Angel Island, temporary batteries of wood and earth were constructed at points Stewart, Knox, and Blunt (cannons were mounted at the first two sites in 1864). At Point San Jose, which is currently known as Fort Mason, a temporary structure completed in 1864 was much larger. A breast-high wall of brick and mounts for six 10-inch Rodman cannons and six 42-pounder banded James rifles were built on the site. No traces of the temporary structures remain today. However, at Point San Jose, 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.1 During the Civil War, advances in weapon technology began to influence how coastal fortifications were constructed. The development of rifled guns, larger smooth bore cannon, and iron-clad warships made the expensive brick and masonry forts obsolete. The Army responded by building the smaller, cheaper earthwork batteries found at Angel Island, Alcatraz, Point San Jose, and Lime Point. The only remaining example of these temporary fortifications is located at Point San Jose (presently known as Fort Mason).1 
NPS photo Post-Civil War Period The period following the Civil War was a time to incorporate the lessons learned on the battlefield, and to apply them to enhance the defense capabilities of coastal fortifications. The most obvious lessons were that only large rifles, and Rodman smoothbores of at least 15-inches, proved effective against armored vessels, that masonry works were also vulnerable to such weaponry, and that earthwork barbette batteries were not only the most resistant to such fire but were also the most cost-effective to build. These discoveries prompted major changes to the seacoast defenses immediately following the Civil War. Earthworks batteries like East and West batteries at the Presidio reflect the new engineering strategy for seacoast fortifications.1 In spite of the drive to improve the defenses around the Golden Gate, most efforts were never completed; funding was scant and rapid advances in military technology were rendering new fortifications obsolete before they could be built. It was during this period that construction began on Battery East, which exemplifies the smaller, more economical coastal fortifications built in the post-Civil War period. Although Battery East was completed in 1872, its cannon were not placed until nearly twenty years after its construction.1 1. Freeman, Haller, Hansen, Martini, and Weitz. Seacoast Fortifications Preservation Manual. Golden Gate National Recreation Area, July 1999. 
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Last updated: March 19, 2015