Historic California Posts, Camps Stations and Airfields
Milagra Military Reservation
(San Francisco Defense Area Site SF-51, less Integrated Fire Control Site (SF-51C]; Battery Construction Nos. 130 and 244, SCR-296 Radar Set No. 9)

Now a part of the Golden Gate National Recreation Area (GGNRA), Milagra Ridge was the southern-most coastal defense work built to defend the entrance to San Francisco Bay. A 6" gun emplacement was built here during World War II. A 16" gun emplacement similar to one at Fort Funston was to be built but it was canceled. Later, the area was used as a launch site for a Nike missile battery. The deserted Battery 244 several fire control stations and the buried Nike bunkers remain at this undeveloped park.
Source: Mark J. Berhow
by Sgt. Maj. (CA) Dan Sebby, Military Historian, California Military Department
On 14 June 1940, the U.S. Army acquired 5.521 acres of land to establish a cable landing and fire control stations for Fort Cronkhite's Battery Townsley, Fort Barry's Battery 129 and Fort Funston's Battery Richmond P. Davis. A fire control station for Milagra Ridge's Battery 244 was also on the reservation. Connecting these fire control stations to the headquarters at Fort Winfield Scott and other harbor defenses was a waterproof telephone cable that ran offshore and came ashore at the Site. There was also a small power plant (Building 234) that provided electrical service to these fire control stations.

From 14 June 1942 until 3 June 1943, the U.S. Army acquired an additional 322.45 acres through direct purchase and Federal condemnation process. Construction on the fortified Battery Construction No. 244 began in 1943 and was completed in 1944. However, the two 6-inch rifles previously located at Fort Columbia, Wash., were not mounted until 1948. The removal of these two guns in 1950 marked the end of static fortifications defending the San Francisco Bay (Golden Gate National Recreation Area 1999).

The T2M1 6-inch Rifle mounted on the M4 Shielded Long Range Barbette Carriage as used at Battery Construction No. 244.
Also located at the Site during World War II and the immediate post-war period was an SCR-296 radar set which provided additional fire control data to the Harbor Defenses of San Francisco. It was located on top of the hill to the southeast of Battery Construction 244. The Site was also defended from aircraft by two M1 40mm mobile antiaircraft guns (positions number 29 and 30) and five 0.50-caliber antiaircraft guns (http://www.cdsg.org, 2005).

In addition to Battery Construction No. 244, there was a plan to build a battery that would have mounted two 16-inch rifles known as Battery Construction No. 130. However, World War II ended before construction on the battery could begin. An additional fire control station for Fort Barry's Battery Construction No. 129 was also built during World War II to the northwest of Battery Construction No. 244.

After the disarming of Battery Construction No. 244, the Site became an inactive installation. According to audited USACE real estate maps, the Site was transferred to the U.S. Navy 31 October 1951 in what appears to be a large transfer of land between the two services. However, the Site was removed from the transfer by the Secretary of the Army on 28 November 1952.

In 1956, the U.S. Army established an air defense missile site on the Site officially known as San Francisco Defense Site SF-51. As with all U.S. Army Air defense missile sites of this period the missile battery was divided into three functional areas.

The Administrative Area (SF-51A) contained the Site's administrative and support functions. This included troop housing and messing, recreational facilities, battery administration, supply buildings, and vehicle maintenance facilities. The buildings were of a standard concrete block construction and were heated by fuel oil (Morgan and Berhow 2002).
Administrative Area (SF-51A) circa 1958

The Control Area (SF-51C, also known as the Integrated Fire Control area) was the location of the Site's radar and fire control systems. The Control Area was located 1-1/2 miles to the southeast on Sweeney Ridge and allowed for 360-degree "line-of-site" radar coverage by the Site's tracking and search radar systems. The missile tracking radar would "lock-on" to the missiles as they sat on the launcher and follow them from launch to impact with the target. The Control Area was located away from the Launcher Area because the high speed of the Nike missiles would have destroyed the mechanisms of the missile tracking radar. SF-51C is reported separately under a separate history.

The Launcher Area (SF-51L) was located adjacent to and northwest of the Administrative Area and consisted of 8 launchers and 2 magazines (also known as underground storage "bunkers") that held a total of 20 MIM-3 Nike-Ajax multi-stage, surface-to-air missiles. The Nike-Ajax missile required facilities for the fuelling of the Ajax (second-stage) portion of the missile. The liquid fuel used for the Ajax was a combination of dimethyl hydrazine and red fuming nitric acid. The Nike portion (booster or first-stage) used a solid fuel which did not require on-site fueling. The magazines were modified from May 1958 to April 1959 to hold 12 of the larger MIM-14 Nike-Hercules missiles. The Nike-Hercules missile used a much safer solid fuel for both stages. The Nike-Hercules missile could be armed with either a high explosive or nuclear warhead. Additionally, the Launcher Area also consisted of missile and warhead assembly, crew readiness, and security buildings. (Morgan and Berhow 2002).

The Site was garrisoned by the U.S. Army's Battery C, 740th Antiaircraft Artillery Missile Battalion (1956 through September 1958); Battery C, 4th Missile Battalion, 61st Artillery Regiment (September 1958 through July 1959); and Battery D, 2nd Missile Battalion, 51st Artillery Regiment (July 1959 through June 1963). The California Army National Guard's Battery A, 1st Missile Battalion, 250th Artillery Regiment (1st California) (After 1966, Battery A, 1st Battalion (Nike-Hercules), 250th Air Defense Artillery Regiment (1st California)) garrisoned the Site from June 1963 until April 1974 when the garrison was inactivated and the Site was deactivated (Morgan and Berhow 2002).
1940 Program and World War II Temporary

 Battery Name

 Number of Guns

 Type of Gun

 Type of Carriage




Battery Construction 244


 6 inch T2M1

 Shielded Long Range Barbette M4




Battery Construction 130


16 inch

 Casemated Long Range Barbette

 Not Built


Battery Construction No. 244
by Justin M. Ruhge
Construction 244 was located on Milagra Ridge south of Fort Funston and behind the town of Pacifica. Like its counterpart at Fort Miley, Construction 243, it was started late in 1943 and not completed by the end of World War II. Construction 244 consisted of two 6-inch breech-loading rifles on barbette mounts surrounded with a two-inch thick steel shield. The two guns were 200 feet apart and separated by an earth-covered concrete magazine and plotting and control rooms.
Milagra Ridge was a site planned for a second 16-inch battery designated Construction 130, which was not started.
During World War II fire control stations and radar installations were located on the remote ridge.
After the war Construction 244, which had been completed, was like 243 turned over to the Navy. The Navy was newly designated as the protector of the minefields. Construction 244 was kept in the service for that purpose until about 1950 when the minefields and the gun batteries were considered obsolete.
BCN-200-Series Battery Layout
An Artist's Rendering of a Standard Two Gun 6-Inch Battery Showing Layout Details. Artwork by Gerald W. Butler.
Taken From of 1940 by Robert D. Zink,
The Six-Inch Part of the Modernization Program,
Coast Defense Study Group Journal, Vol. 8, No. 2, pgs. 21-39, May 1994.
SCR-296 Radar Set No. 9 Supporting Battery 244
Typical installation of an SCR-296 radar set.

Description: Fixed Coast Artillery gun-laying medium wave radar, assigned to modern 6 inch or larger batteries.
Uses: Set is designed to track a surface target in range and azimuth. Data are sent to the plotting room and used in firing. An SCR-296-A normally is assigned to one battery, but may furnish data to more. Works with IFF RC-136-A.
Performance & Sitting: Range is shown on "A" scope. The target is tracked in azimuth with a pip matching oscilloscope or a zero-center meter. Range accuracy is about ± 30 yards while azimuth accuracy is about ± 0.20 degree under the best conditions. The set has a dependable range of 20,000 yards on a destroyer size target when employed at a height of 145 feet. Site should be not less than 100 feet above sea level; 150 to 500 feet is recommended.
Mobility: Shipment includes areas and separate generator. When crated the total weight is 91,763 lbs. Largest unit is 5,270 lbs.
Installation: SCR-296-A includes a tower, an operating building, and two power plant buildings. The tower is obtainable in heights of 25, 50, 75, and 100 feet. Concrete floors must be put in locally.
Personnel: Operating crew consists of 5 men in addition to a power plant operator and maintenance man who should be available at all times.
Power: Primary power of 2.3 KW is supplied by PE-84C -- commercial or auxiliary 110 V, AC single phase. Generator needs high octane gasoline.

Information from Naval History Library Online.

Report of Completed Works - Seacoast Fortifications: SCR-296 Seacoast Radar Set No. 9

San Francisco Defense Area SF-51
by Sacramento District, US Army Corps of Engineers

The Milagra Ridge Military Reservation (Nike Site SF-51L) is situated approximately seven miles south of San Francisco in Pacifica, San Mateo, CA. The total acreage was 330.01. There were 327.97 fee acres, 0.58 license acres, and 1.46 easement acres. The site was acquired in 1942.

The Milagra Ridge Military Reservation site was originally used for coastal defense purposes, fire control station, and most recently as a launcher and administrative area of Nike Site SF-51. This site was used by the U.S. Army Air Defense Command.

Between July 11, 1946 and May 10, 1962, 73.11 acres were disposed of. Of the remaining 256.90 acres, a portion of Nike Site SF-51 (36.48 acres) was declared excess in 1972 and was transferred to the Department of the Interior, and subsequently transferred to the City of Pacifica in May 1974. The U.S. retained 220.42 acres. The 73.11 acres disposed of in 1962 are currently privately held: 28.79 acres are in residential development and 44.32 acres are under development.


The Nike-Ajax and Nike-Hercules Missiles
The Western Electric SAM-A-7/M1/MIM-3 Nike Ajax

The Nike Ajax was the world's first operational surface-to-air guided missile system. Its origins lay in the immediate post-war time, when the U.S. Army realized that guided missiles were the only way to provide air-defense against future fast high-flying bombers. Western Electric became the prime contractor for the XSAM-G-7 Nike missile system and Douglas as the primary subcontractor was responsible for the missile airframe.

The first unguided Nike missiles were fired in 1946, but problems with the original multi-rocket booster (eight solid-fuel rockets wrapped around the missile tail) soon led to delays in the program. In 1948, it was decided to replace this booster pack with a single rocket booster, attached to the back of the missile. The main propulsion of the missile was a Bell liquid-fueled rocket motor, and the flight path was controlled by the four small fins around the nose. In November 1951, the first successful interception of a QB-17 target drone succeeded. The first production Nike (which had been redesignated SAM-A-7 in 1951) flew in 1952, and the first operational Nike site was activated in 1954. By this time, the missile had been designated by the Army as Guided Missile, Anti-Aircraft M1. The name had changed to Nike I, to distinguish it from the Nike-B (later MIM-14 Nike Hercules) and Nike II (later LIM-49 Nike Zeus). On 15 November 1956, the name was finally changed to Nike Ajax.

The Nike Ajax missile used a command guidance system. An acquisition radar called LOPAR (Low-Power Acquisition Radar) picked up potential targets at long range, and the information on hostile targets was then transferred to the Target Tracking Radar (TTR). An adjacent Missile Tracking Radar (MTR) tracked the flight path of the Nike Ajax missile. Using tracking data of the TTR and MTR, a computer calculated the interception trajectory, and sent appropriate course correction commands to the missile. The three high-explosive fragmentation warheads of the missile (in nose, center, and aft section) were detonated by ground command, when the paths of target and missile met.

One of the major disadvantages of the Nike Ajax system was that the guidance system could handle only one target at a time. Additionally, there was originally no data link between different Nike Ajax sites, which could lead to several sites engaging the same target. The latter problem was eventually solved by the introduction of the Martin AN/FSG-1 Missile Master command-and-control system, with automatic data communication and processing. Other problematic features of the Nike Ajax system were the liquid-fuel rocket motor with its highly toxic propellants, and the large size of a complete site with all components, which made Nike Ajax to all intents and purposes a fixed-site air defense system.

By 1958, nearly 200 Nike Ajax sites had been activated in the United States. However, the far more advanced MIM-14 Nike Hercules soon replaced the Nike Ajax, and by late 1963, the last Nike Ajax on U.S. soil had been retired. In 1963, the Nike Ajax had received the new designation MIM-3A. Despite the use of an MIM (Mobile Intercept Missile) designator, the mobility of the Nike Ajax system was more theoretical than actually feasible in a combat situation.

The MIM-3A continued to serve with U.S. overseas and friendly forces for many more years. In total, more than 16,000 missiles were built.


Nike Ajax and Nike Hercules Missiles (NARA)

Western Electric SAM-A-25/M6/MIM-14 Nike Hercules

The Nike Hercules was the only nuclear-armed surface-to-air weapon, which was operational with the U.S. Army. Development of an improved Nike missile began in 1952, with the primary goal to develop a missile with a significantly higher performance than MIM-3 Nike Ajax (then known simply as Nike), which could still be used with the existing Nike ground equipment. After it had been shown that the Nike Ajax could not be equipped with then existing nuclear warheads, nuclear armament became another goal for the new missile. The SAM-A-25 Nike B program was formally established in June 1953. As with Nike Ajax, Western Electric was prime contractor, and Douglas was responsible for the missile airframe.

The Nike B (renamed Nike Hercules on 15 December 1956) used many components of the Nike I (Nike Ajax). The booster consisted of four Nike Ajax boosters, and the original design used 4 of Ajax' liqued-fuel rockets as sustainer propulsion. However, the first flight tests with the liquid-fuel sustainer in 1955 proved very troublesome, and a solid-fueled sustainer rocket was eventually used. The first successful interception of a drone target occurred in 1956, and in 1957 the new solid-fuel sustainer flew for the first time. Nike Hercules used the same command guidance as the MIM-3 Nike Ajax, with essentially the same ground components.

The first production Nike Hercules missiles were delivered in 1958, and quickly replaced the Ajax on many Nike sites. By then, the Nike Hercules had been designated as Guided Missile, Air Defense M6. The M6 could be equipped with either an M17 (a.k.a. T45) blast-fragmentation warhead, or a W-31 nuclear fission warhead with yield selectable as 2 kT or 40 kT. The missile performance was such that even very high-flying bombers could not escpe the Nike Hercules. Capability against low-level targets remained rather limited, however.

As the Nike Hercules began replacing the older Nike Ajax, work was underway to improve the acquisition and tracking radar capabilities to fully exploit the missile's greater performance. The major improvement in what was called the Improved Hercules system was the new L-band acquisition radar, called HIPAR (High-Power Acquisition Radar). The TTR (Target Tracking Radar) and TRR (Target Ranging Radar) were also improved, having better ECM resistance. The missiles of the improved Improved Hercules system were designated as M6A1. In June 1960, an Improved Hercules achieved the world's first successful interception of a ballistic guided missile, when a MGM-5 Corporal SRBM was shot down. The new radars were also far more compact than the original ones, which made moving a Nike site a least somewhat practical for the first time. Lastly, Improved Hercules introduced a viable surface-to-surface capability to the Nike system. The first Improved Hercules systems were installed at Nike sites in June 1961.

In 1963, the M6 and M6A1 missiles were redesignated as MIM-14A and MIM-14B, respectively. The MIM-14C (introduced in 1972) was a modified MIM-14B with an improved missile guidance section for higher manoeuverability and better ECM resistance.

All in all, the U.S. Army established 145 Nike Hercules sites over the years. Production of the nuclear-armed missiles ended in 1964, and gradual phase-out of the MIM-14 began in the late 1960's. The Army originally planned to replace the Nike with the new MIM-104 Patriot missile, but this plan was not implemented in the USA. Therefore, after the last active Nike Hercules sites in the continental U.S. had been deactivated in 1974, there are no long-range air-defense missiles fielded in the U.S.. In Europe, the U.S. Army retired its last MIM-14 units in 1984, when the MIM-104 Patriot was introduced.

In total, more than 25,000 Nike Hercules missiles of all wersions were produced, most being of the MIM-14B variant.
Source: Directory of U.S. Missiles and Rockets, http://www.designation-systems.net/
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Reports of Completed Works - Seacoast Fortifications: Milagra Military Reservation
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Updated 13 October 2015