Historic California Posts, Camps, Stations and Airfields
Coast Guard Training Center, Petaluma
(Two Rock Ranch Station)
Entrance to Coast Guard Training Center Petaluma, circa 2008.

The Training Center operates no less than 10 schools offering 50 courses to approximately 4000 students a year. In addition to Coast Guard military and civilian employees, the Training Center also provides training to international students. Located in the rolling hills of the Two Rock Valley, this large training command provides apprentice level training for seven enlisted career fields and manages CG-wide training in leadership and Total Quality Management for personnel at all levels of the organization. The unit provides performance technology courses in basic instructor skills and course designing skills. The Training Center also provides courses for emergency medical technicians, maritime law enforcement, and computer operation and management. The Training Center consists of over 800 acres with 219 buildings, including 129 family units, a fully staffed clinic, a chapel, a small police and fire department, and over 200,000 square feet of training facilities.
In 1942, the Army purchased Two Rock Ranch and built a Communications Station. The station's location was ideal for monitoring Japanese communications during World War II. Operations at the station were top-secret.
During the Vietnam War, the station added training to it's mission. Portions of the base were transformed into a Vietnamese village to train troops headed for Vietnam. In the late 1960's, satellites and other technological advances made the listening post obsolete and preparations were made to close the base.
With the Vietnam War in progress, the Coast Guard faced increased training demands. The Training Center at Governor's Island in New York became overcrowded, so the Coast Guard started looking for a suitable site for a new training center. In the spring of 1971, The Coast Guard learned of the closing of Two Rock Ranch Station. Officials visited the property and were impressed with the station. Although the California Highway Patrol and an Indian group were interested in the land, the Coast Guard was awarded the station. On July 1, the Coast Guard relieved the Army and took possession of the station.
Soon after taking over the property, it was decided that the name "Two Rock Ranch" was not suitable for a Coast Guard Base. In spite of interest in retaining "Two Rock" as part of the new name, the base was renamed Coast Guard Training Center, Petaluma. Interestingly, one reason Petaluma was chosen over Two Rock was that Petaluma appeared on many maps whereas Two Rock did not. This was considered important for Coast Guard members who would be trying to locate the base when traveling to it.
Immediately after the training center opened, Subsistence Specialist school began training Coast Guard cooks. Soon after that, Storekeeper school opened. Approximately 6 months later the Radioman School opened. In April of 1972, less than a year after it opened, the base was fully loaded with students.
The nearest town to the Training Center is Petaluma, the second largest and southernmost city of Sonoma County. Started as a riverbank hunting camp in the 1850's, Petaluma quickly grew into an agricultural, trade and industrial hub that by 1918 claimed the title of "Egg Basket of the World". Petaluma was the richest city of it's size in the United States during the 1920's partly because of the cheap transportation for agricultural products offered by the Petaluma River. Today Petaluma still retains some of it's agricultural flavor, but it is becoming a nice bedroom community of the Bay area job market. Downtown has been renovated and cafe's abound for the weekend antique shoppers who flock to the wide assortment of shops. Housing in Petaluma is a mixture. Newer homes on the east side of Hwy 101 and older ones on the west. Filmmakers especially like the older, well kept west side for it's quaint, all-American looks. The city has had parts in movies since the 1940s, including "Basic Instinct","Peggy Sue Got Married", and "American Graffiti"
Copied with permission from globalsecurity.com
US Army Corps of Engineers Chronological Site Summary for Two Rock Ranch Station

On 7 August 1942, Two Rock Ranch Station was established as a primary monitoring station under the command of the Chief Signal Officer. The area had been dairy and poultry farms prior to War Department purchase of the nine tracts. The first contingent of troops to occupy the installation included two (2) officers and 45 enlisted men from Fort Monmouth, New Jersey, who arrived in October 1942. The only billeting consisted of tents while the former ranch houses were converted for use as administrative and operational facilities.

The primary mission of Two Rock Ranch Station was the interception of enemy radio transmissions with a secondary mission of training radio operators for service in the Pacific Theater. By 9 April 1943, 23 buildings had been constructed and the number of personnel assigned had been increased from 200 to 521 men. All buildings were camouflaged to give the appearance from the air that the installation was nothing more than a working ranch. A haystack covered the water tower, furrows were plowed and planted, and an artificial cow made of feathers over a wire frame was placed in a pen.

In October of 1943, a contingent of approximately 100 Women's Army Corps (WAC) personnel was assigned as radio operators. These personnel stayed until the end of the war.

At the end of World War II, Two Rock Ranch Station was redesignated as a special installation under the command of the Army Security Agency (ASA). The mission of monitoring radio transmissions for intelligence purposes remained the same. An ambitious program of modernization was begun wherein most of the original ranch buildings and World War II structures were replaced by more modern, permanent structures.

On 25 April 1947, a tract containing 35.37 acres was transferred from the War Department to the War Assets Administration (WAA) . An additional 5.36 acres was quitclaimed to the Two Rock Union School District on 11 December 1951.

Advances in satellite technology eventually made the antenna fields at Two Rock Ranch Station obsolete and the installation was closed on 30 June 1971. On 29 July 1971, the Department of the Army transferred the remaining 835.68 acres to the U.S. Coast Guard (USCG), Department of Transportation (DOT) for use as a USCG training center. The USCG also obtained the 35.37-acre tract that had been transferred to the WAA in 1947.

In 1985, DOT conveyed two parcels consisting of 30.89 acres and 35.37 acres to private individuals. An additional 8.56-acre tract was deeded to the Two Rock Union School District.
Historic Military Munitions Usage

Due to the nature of the site, a radio receiving station, and the highly classified nature of the work performed, the use of military munitions on the site was extremely limited. During World War I1 those individuals assigned guard duty were issued small arms. These consisted of .45 caliber submachine guns and 12-guage shotguns. Ammunition and weapons were stored and issued at the guardhouse. There were no ranges during this period.

Sometime prior to 1952, two ranges consisting of a double skeet range and a 1,000-inch small arms range were constructed. The double skeet range is still in use by the U.S. Coast Guard. The small arms range was recreational in nature and was also used with M1 carbines by Boy Scouts. This range continued in use until at least 1961. Qualification for record was not performed at Two Rock Ranch Station but at other military facilities in the San Francisco Bay area.

Two magazines, buildings 539 and 540, were constructed in 1968. These were identified as ready magazine and a fixed ammunition magazine. These two magazines were used to store shotgun ammunition for the skeet range. Although the U.S. Coast Guard did not use these magazines, they continued to exist at least until 1984.

An indoor pistol range was built in 1965. This range was identified as Building T831. The U.S. Coast Guard demolished this building in 1997 and the bullet trap was environmentally mitigated. No further action is contemplated for this site.

A mock 'Vietnam Village' was constructed of local materials in the late 1960s. This mock village was used in a training course for ASA personnel in dealing with the conditions in Vietnam. According to several eyewitness accounts, only blank small arms ammunition was used in these activities.
Source: Archives Search Report, US Army Corps of Engineers, Rock Island District, October 2003.
Two Rock Ranch family housing area with the station's antenna farm and water treatment ponds in the background. Circa 1970.
Extracts from Historical Data Cards, US Army Center of Military History
Two Rock Ranch Station
The Primary Monitoring Station under construction at Two Rock , Petaluma, California, is classified as an installation under the command of the Chief Signal Officer in accordance with the provisions of para. 6 a (4)(a) AR 170-10, SPX (7-24-42)MR-M-P. dated August 7 , 1942 (S). /322.08

Two Rack Ranch Station is a subordinate agency of the Signal Security Agency, Washington, D.C., per 1st OCSigO dated 25 Aug 44, SPSEC 321 Sig C Org (19 Aug 44) (C).

Two Rocks Ranch Station, Petaluma, California, is reclassified,, effective 15 Sept. 1945, as a special installation under the control of the Chief, Army Security Agency, in accordance with AR 170-10, para 63(5), pursuant to authority contained in AG 322 (4 Sep 45) OB-S-B-M, dated 6 Sept. 1945. per AG. 323.3 (17 Sep 45) OB-S-B, dated 21 Sept. 1945. Any previous instruction: in conflict with the foregoing are superseded.

Effective 12 June 1946, the Two Rock Ranch Station. Petaluma, Calif. is reclassified as a class II activity and under the jurisdiction and control of the Director of Intelligence in accordance with WD Cir. # 135, 1946 - per WD Cir. # 169 dated 11 June 1946. Rescinded. Eff 9-25-46 reclass II install under Dir./Intell in accord/WD Cir.138,46-per WD Cir. #292, dtd,9-25-46.

Two Rock Ranch Station; ,Petaluma, Calif., a Class II installation, is hereby classified as "SECRET" - per AG 680.1 (6 Sep 46)A0-1-WDGID-M, dated 12 September 1946. RESCINDED: AGAO-I (M) 680.1
Photographic Laboratory, Two Rock Ranch Station, Petaluma, California shown on list of photograhic laboratories as a class II installation under the jurisdiction of the Director of Intelligence, WDGS - per Ltr., Hq Sixth Army, Presidio of San Francisco, California, 6 November 1946.

ASU, Two Rock Ranch, Petaluma, Calif. reorganized under T/D #206-1900 dated 1 Oct 47 - per Sixth Army T/D for person: authorized in bulk.

ASU #6900, Two Rock Ranch. Petaluma, Calif. is reorganized under T/D #206-1900, Hq Sixth Army, 30 June 1948.

6900 ASU, Sv Det, Two Rock Ranch, Petaluma, Calif. to be reorgnd under T/D #206-1900, Hq Sixth Army, 30 June 49 & 31 Dec 49,

Effective 1 July 1950, the Dispensary, Two Rock Ranch is redesignated the US Army Dispensary, Two Rock Ranch with location Petaluma, California per GO 21, Dept of the Army, 6 July 1950
8602d Administrative Area Unit, Field Station is organized at Two Rock Ranch Station, Petaluma, California, effective 15 May 1950 - per Copy of GO 13, Hq Army Security Agency, 12 May 1950. See also GO 5, Hq Two Rock Ranch Station, Petaluma, California, 15 May 1950.
Is designated a permanent DA installation effective 1 July 1954 - GO 60, DA, 16 Aug 1954
Two Rock Ranch Station, Calif, a Class II installation, ASSIGNED to Army Security Agency is REDESIGNATED as a class III installation effective 1 July 1955 - GO 23, DA, 25 Mar 1955.
Two Rock Ranch Station, Calif, a Class III installation, ASSIGNED to Army Security Agency is REDESIGNATED as a class II installation - GO 35, DA, 25 Jul 1957
TD 66-6350-00 is ASSIGNED to US Army Dispensary, Two Rock Ranch Station at Petaluma, Calif effective 1 Jan 1959 - GO 203, Sixth US Army, 29 Dec 1958.
TD 93-8602 is WITHDRAWN and TD 86-9319 is ASSIGNED effective 1 Mar 1959 - Ltr, GAS23 250/29(17), US Army Security Agency, Arlington Hall Station, 2 Feb 1959.
Two Rock Ranch Station, California is to be DISCONTINUED effective 30 Jun 1971 - DCSLOG ltr 21 Jun 1971.
Two Rock Ranch Station, California is DISCONTINUED effective 30 Jun 1971 - GO 86, USASA, 26 Apr 1971.
Effective 30 June 1971, Two Rock Ranch Station, California, a class II installation under the jurisdiction oftheCommanding General, US Army Security Agency, is placed in an inactive status - GO 29, HQDA, 24 June 1971
US Army Garrison, Two Rock Ranch Station
US Army Garrison, Two Rock Ranch Station is ORGANIZED at Two Rock Ranch Station, Petaluma, Calif as a separate class II activity, ASSIGNED TD 86-9319-O2, 1961 with an authorized strength of 6 OFF, 88 ENL,, 46 CIV, ASSIGN] to 2d US Army Security Agency Field Station, Two Rock Ranch Station, Petaluma, Calif effective 1 Jul. 1961 - GO 32, US Army Security Agency, 15 Jun 1961.

US Army Garrison, Two Rock Ranch Station is DISCONTINUED effective 1 May 62 - GO 23, US Army Security Agency, 13 Apr 62.
Main gate of the US Army's Two Rock Ranch Station, circa 1968.

Extract, War Department Inventory of Owned, Sponsored and Leased Facilities, 1945

Units Assigned to Two Rock Ranch Station



 Army Station List 1 June 1943

Army Service Forces 

  • Primary Monitoring Station

Western Defense Command

  • 107th Cavalry Regiment (Mechanized)
    • 2nd Battalion
      • Headquarters and Headquarters Troop
      • Troop C (less three platoons)
      • Troop E
  • 673rd Medical Collection Company
 Army Station List 7 April 1945

 Army Service Forces:

  • Primary Monitoring Station
  • Two Rock Ranch Station, Signal Security Agency
  • 62nd Signal Radio Intelligence Company
  • 7916th Service Command Unit (Service Group, Two Rock Ranch)
 Army Station List 7 April 1945

 Army Service Forces:

  • Primary Monitoring Station
  • Two Rock Ranch Station, Signal Security Agency
  • 3959th Service Command Unit (Two Rock Ranch)

Additional Online Information
US Army Corps of Engineers Rock Island District Archive Search Report
Official Training Center Petaluma website
Search our Site!
Search the Web Search California Military History Online
View My Stats
Visitors since 8 December 1998
Questions and comments concerning this site should be directed to the Webmaster
Updated 23 June 2017