The biggest guns in the Harbor Defenses of San Francisco could fire shells weighing more than a ton 26 miles out to sea. Photo courtesy of San Francisco History Center, San Francisco Public Library

Beginning during the California Gold Rush in the 1850s, the U.S. Army had been continually constructing, expanding and modernizing harbor defenses surrounding the Golden Gate and intended to keep an enemy from capturing the port with its strategic military and industrial sites. In the early years, French and British fleets were most feared by American planners, and large masonry forts armed with scores of smoothbore cannon were constructed at Fort Point in the Presidio of San Francisco and on Alcatraz Island in the middle of the bay. During the Civil War and the years immediately following, additional masonry and earthwork fortifications were constructed along both shores of the Golden Gate straits. Well-preserved examples of these semipermanent fortifications can still be seen at Battery East in the Presidio and at Battery Cavallo at Fort Baker.

North of the Golden Gate, hidden in the hills of the Marin Headlands, and south, in the dunes of Fort Funston, guns originally designed for battle cruisers protected the most important military harbor on the West Coast Photo courtesy of National Archives and Records Administration

In the 1890s the army began a major modernization of the Nation's coastal fortifications and, because of its strategic importance, San Francisco Bay was given number two priority behind New York Harbor. (Actually, defense appropriations for San Francisco defense projects frequently exceeded those of New York.) This rearmament project resulted in the wholesale scrapping of smoothbore artillery and the introduction of modern breech loading artillery protected in concrete gun emplacements. Construction of these fixed defenses had a dual role: first, the improved fortifications made the Nation's ports much more secure and ready to deal with the threat from modern armored warships; secondly, the strong shore defenses freed up the U.S. naval forces from their reluctant role as "floating coastal forts." This strategic change allowed our navy to sail the globe freely and extend our military presence--and U.S. influence--to foreign countries. By 1910, nearly 120 coast artillery guns were mounted in the Harbor Defenses of San Francisco. Ranging in size from three-inch rapid-fire weapons to 12-inch long-range guns, these fortifications were designed to meet the threat of any size vessel from a small patrol boat to a heavily armored battleship. These new weapons and fortifications would form the backbone of San Francisco's coastal defenses until after the end of World War II.

As Europe headed deeper towards war in the 1930s, isolationist America reluctantly began to upgrade its coastal fortifications once again. In San Francisco, this program lead to the construction of two batteries mounting the largest guns then in American arsenals: 16-inch caliber rifled guns mounted on high elevation carriages, capable of firing 2,100-pound projectiles nearly 26 miles. To protect the weapons against the growing threat of aerial bombardment, each battery of two guns was constructed as a subterranean fortification with the guns aiming out from the sides of heavily camouflaged, manmade hills. Up to 20 feet of overhead concrete and earth cover provided protection for the guns themselves along with a labyrinth of connecting corridors, ammunition magazines, power plants, crew spaces, and assorted storage rooms. To protect the new batteries, antiaircraft guns were concentarted nearby to ward off attacking enemy aircraft.

In the wake of the war, the huge guns were scrapped, each one providing as much as 300,000 pounds of high quality steel to help fuel the postwar economic boom. The ascendancy of air power made traditional coast defense artillery obsolete. Photo courtesy of Golden Gate National Recreation Area, Interpretive Negative Collection

Completed in 1940, Battery Davis at Fort Funston and Battery Townsley at Fort Cronkhite were the prototypes for all subsequent fortification designs adopted by the U.S. Army. On the eve of World War II, these two batteries formed the state-of-the-art defenses not only of San Francisco but also of the entire United States.

On December 7, 1941, the Harbor Defenses of San Francisco Bay comprised a mixture of modern batteries as typified by Batteries Davis and Townsley; aging--but still potent--coast artillery emplacements constructed at the turn-of-the-century; mobile tractor drawn field artillery and antiaircraft guns; and the underwater minefields that still protected the shipping channels. Manning these defenses were an assemblage of "old army" regulars from the Sixth Coast Artillery Regiment, newly-formed units such as the 18th, 54th and 56th Coast Artillery Regiments, and National Guard Regiments from as far away as Minnesota and Texas. When news reached San Francisco of the Japanese attack on Pearl Harbor, all off-duty personnel were recalled to their units and the harbor defenses put on full alert. Soldiers moved out of their barracks and into the batteries, and began filling sandbags, stringing barbed wire and constructing beach defenses at a fevered pace. Up and down the coast, observers in tiny concrete observation posts scanned the horizon for the approach of a Japanese fleet that would never come.

Under camouflage netting, to hide the emplacement from aerial observation, gunners drill on one of the six-inch guns of Battery Chamberlin at Baker Beach in San Francisco--only yards away from the swank homes of the Sea Cliff district. Photo courtesy of Golden Gate National Recreation Area. PAM Prints Collection.

As the days and weeks progressed, the initial fear of imminent invasion settled into a long-term commitment to defend the harbor by every means possible. Mobile antiaircraft guns, searchlights and radars were positioned on virtually every hill and knoll overlooking the Golden Gate. The U.S. Navy stretched an antisubmarine net across the inner harbor extending from the Marina in San Francisco to Sausalito in Marin, and stationed a navy tugboat to open and close the net to allow friendly shipping to pass. Soldiers assigned to the fortifications and observation stations constructed extensive earthwork trenches on the hillsides near their batteries, and in some cases tunneled into hillsides to construct unauthorized but comfortable underground quarters. Everywhere, camouflage paint was daubed on concrete batteries and wood barracks, and acres of camouflage nets were stretched over fortifications to obscure their presence from high flying enemy planes. Overhead, navy blimps armed with depth charges patrolled offshore waters searching for Japanese submarines but only attacked the occasional unfortunate whale.

The command center for all these activities was an underground facility covertly constructed at Fort Winfield Scott in the Presidio of San Francisco and dubbed the Harbor Defense Command Post/Harbor Entrance Command Post (HDCP/HECP). The HDCP/HECP was little discussed but its role was crucial, for here inside the bomb proof command center army and navy senior staff coordinated their resources both to defend the bay against enemy sea or air attack (the army's role) and also to track and coordinate all shipping traffic in and out of the Golden Gate (the navy's responsibility).

Artillerymen of the 54th Coast Artillery Regiment (Colored), as it was officially designated at the time, fire a 155GPF mobile gun from a beach in the Marin Headlands. This African American outfit was quartered at the barracks overlooking Rodeo Beach at Fort Cronkhite before being shipped to, of all places, Peru to protect against a perceived Japanese threat there. Photo courtesy of Golden Gate National Recreation Area. PAM Prints Collection.

No enemy has ever attacked San Francisco, and by 1944 it was obvious to the army-navy commanders that invasion was a far distant likelihood. The soldiers of the harbor defenses were needed on battlefronts elsewhere, and starting that year the HDSF began to phase out its operations. With the signing of the peace treaty with Japan in 1945 the army reevaluated its need for fixed defenses, especially in light of a new age of long-range bombers and nuclear weapons. The phase out was speeded up, and by 1948 the last of the army's San Francisco coastal artillery fortifications had been scrapped.

Today, the remains of "Fortress San Francisco" can still be found throughout the Golden Gate National Recreation Area. In the Presidio of San Francisco, Battery Lowell A. Chamberlin at Baker Beach displays a rare six-inch rifle on a 1903 disappearing carriage, and an adjacent display gallery tells the story of the bay's harbor defenses. Fort Point, a veteran of the Civil War, was pressed into use during World War II for a battery of three-inch guns, and its museum also tells the story of the harbor defenses of San Francisco. At Forts Funston and Cronkhite, the empty casemates of Batteries Davis and Townsley can still be explored although their unlit interiors are closed for safety reasons. Below Battery Townsley at Rodeo Beach in Fort Cronkhite, visitors can see the preserved 1940s "mobilization barracks" complex where the coast artillery soldiers lived.

Numerous concrete and steel "pillboxes" still crown many sites with the best views along the coastline of the Golden Gate National Recreation Area. Officially known as base-end stations, the soldiers were there to spot the positions of ships offshore and communicate with plotting rooms that supplied firing data to the big guns. Photo courtesy of Golden Gate National Recreation Area. PAM Prints Collection.

Across from Fort Cronkhite is Fort Barry, site of several 1900-era gun batteries that were armed during World War II. Many of these batteries still display remnants of their green-and-ochre camouflage schemes applied shortly after Pearl Harbor. Also at Fort Barry is Battery Elmer J. Wallace, a 12-inch battery that was extensively rebuilt with overhead cover during World War II and now appears much like a scaled-down version of Batteries Davis and Townsley.

Throughout Golden Gate National Recreation Area are dozens of observation posts used by coast artillery troops. Officially known as "base end stations," these tiny structures housed a crew of observers whose job was to search the horizon for the approach of enemy ships and, in the event of attack, direct the gunfire of the big guns through telephone communication. These stations stretch along the San Francisco coastline from Point Reyes in the north to Half Moon Bay in the south. Some of the best examples can be found at Fort Cronkhite above Battery Townsley; at Fort Barry near Battery Mendell; and at Fort Funston near Battery Davis.

The plotting room in each gun battery was where data from the spotters at base-end stations was received by telephone. Rapid trigonometric calculations resulted in range and bearing date being transmitted to the big guns--and in accurate fire, if all went well. Photo courtesy of San Francisco History Center, San Francisco Public Library

Perhaps the most visible remnant of the army's defensive system is the land itself, for in their efforts to construct ever more far-flung fortifications the U.S. Army purchased large tracts of land overlooking the Golden Gate and its approaches. Kept out of private hands, these lands eventually formed an unintentional but invaluable "green belt" around the entrance to San Francisco Bay. In 1972, Congress created the Golden Gate National Recreation Area and included these lands within its boundaries. Today, the former World War II harbor defense posts of Forts Funston, Miley, Winfield Scott, Baker, Barry and Cronkhite provide some of the most spectacular and unspoiled open space surrounding any American city. Combined with the even earlier military posts of Alcatraz Island, Angel Island, Fort Mason and the Presidio of San Francisco, the U.S. Army handed down to today's generation a gift of urban parkland truly unrivaled anywhere.

Essay by John A. Martini.