A Brief History of Fort Rosecrans
The original fortification at Point Loma was built by the Spaniards and called Castillo (Spanish for fort) Guijarros (Spanish for shingle) sometime between 1797 and 1798. It was a low earthen-walled fort at La Punta de los Guijarros, which is now called Ballast Point and is now part of the Point Loma Submarine Base. By 1840, the fort fell into disuse and was sold to a local landowner for $40. There are two surviving cannons from the Spanish time period; one is mounted at Old Town State Park, and the other is located at the Fort Stockton site inside Presidio Park.
On Feb. 26, 1852 an Executive Order of the President of the United States set aside the parcel of land that contained Castillo Guijarros for military purposes. Initially, the executive order had no funding, so it wasn’t until 1873 that the U.S. Army began to install cannons in the remains of Castillo Guijarros. The project progressed slowly until 1890 when a Congressional order supplied the money to complete the work. The new fort was completed in 1898 and was renamed Fort Rosecrans.
The actual number of men stationed at the fort varied widely during the next 17 years, depending on the international demands on the U.S. military. For the most part Fort Rosecrans acted as temporary housing for troops that were needed elsewhere. These other locations included China, for the Boxer Rebellion from 1899 to 1901, and Otay Mesa, when President Wilson reacted to Pancho Villa’s New Mexico raids in 1916 by sending soldiers from Fort Rosecrans to prevent Mexican raiders from crossing the border.
During World War I, Fort Rosecrans was fully staffed with four 10-inch guns, two 5-inch guns, two 3-inch guns, and eight 12-inch mortars. In addition, the Army trained two antiaircraft batteries and one ammunition train battalion at the fort before sending them to France.
By 1922, post-war cuts in military spending meant Fort Rosecrans was placed on “caretaker” status, with minimal staffing levels and almost no activity. During this time, the fort was the temporary home of several non-artillery Army units. The most notable were the Sixth Infantry Brigade in 1930 and A troop of the 11th Cavalry in 1931. This was also the time when Fort Rosecrans earned its reputation as being an “old soldier’s home.” Because of San Diego’s good weather, the fort became a desirable duty station and only senior servicemen would have enough experience and seniority to be posted to Fort Rosecrans.
By the late 1930s the threat of war in the Pacific was serious enough for the Army to start building new facilities at the Fort. By 1941 several new 8-inch guns and 155mm howitzers were installed, and by 1943 Battery Ashburn, with its two 16-inch “battleship” guns, was complete.
With the end of World War II came the end of the coastal battery as part of America’s strategic defense, and Fort Rosecrans was officially abandoned by the Army. The land surrounding the old Point Loma Lighthouse was turned over to the National Park Service immediately following the war, and by July 1, 1959 the rest of the facilities were turned over to the Navy. Most of the large gun bunkers are now laboratories for SPAWAR and other Navy projects.
What You Should Know About Our Base End Station
Our base end station served two purposes; it housed the battery commander and acted as an observation post. No guns were ever placed inside this bunker.
The upper level acted as the battery commander’s station, where the captain in charge of Battery Ashburn would make his decisions as to how, where, and when the battery would fire. Most of the equipment present in this room would be administrative in nature, e.g. desks, phones. Also present would be a single azimuth scope for verification and identification of targets.
The lower level directly below the upper bunker was a bunk room, so personnel off duty could rest without interfering with those on duty.
The lower forward level was a full base end station, with two azimuth scopes, a depression finder and enough telephones to simultaneously report all the data generated by these instruments.
The azimuth scopes were used to measure horizontal angles towards targets. They were calibrated to read the number of degrees and hundredths of a degree from true south. Minimum crew was two men, one to keep the scope on target, the other to read the bearing angle. These instruments were used in the “horizontal base” system, where this angle would be used in conjunction with azimuth bearings from one or more base end stations to triangulate the location of the target.
The depression finder was used to determine vertical angles. Operated by two men in the same way as an azimuth scope, this instrument was used in the “vertical base” system, where a single base end station could determine the exact location and distance to a target by comparing the angle of the target to the horizon. There is no depression finder present in the base end station today.
All the original permanent mounts for these optical instruments have been removed from the station. The only evidence visible today of these mounts is the roughness in the floor of three areas in the lower forward part of the station.
Actual tracking of the targets happened in the plotting room, an area separate from the base end stations. Inside this room was a semicircular table that represented the field of fire of the guns being controlled. Along the bottom straight edge were several straight edged rulers, fixed so they could rotate, each representing a base end station. When azimuth bearings were reported, these rulers were rotated to the reported angle and where the rulers crossed was the location of the target. These observations were done exactly every 20 seconds and it took three sightings (one minute) to accurately locate a target’s speed, distance, direction of movement, and position. Based on this data, the direction, angle, and the time that the gun would be fired was mathematically calculated and telephoned to the gun position.
To ensure accuracy, there was a set procedure to record these observations. The system was based on sound signals generated by a series of electric bells mounted in each base end station and plotting room. Controlled by a telegraph system, these bells were rung three times per minute (every 20 seconds) simultaneously in every base end station and plotting room. The pattern was one ding 10 seconds before the actual time of the measurement as a preparation signal. Then, at about one second before the reading was required, the bell rang three times, the third ring being the moment when the angle was recorded. This system ensured all the stations were reporting their bearings at exactly the same time.
Last revised 30-Jan-23