Historic Structure Report
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The Earthwork, or Second Fort, was designed by Captain Cuvier Grover, 10th Infantry, in mid-1861. Constructed under the direction of Captain Grover and First Lieutenant William J. L. Nicodemas, 11th Infantry, under the command of Major (Brevet Lieutenant Colonel) William Chapman, 2nd Infantry (Arrott, card 63). The site was selected about August 4, and construction began August 4 or 5 (Oliva, "Frontier Army," p. 332). The detailed inspection of the field work itself and the available maps and photographs by Nicholas Bleser in the 1960s, and his suggestions about the plan of the Second Fort, its probable interior arrangement, and the locations and functions of its outworks, all formed the basis upon which the present plan and detailed inventory was founded. Without his research, fieldwork and insights, the present Base Map of the Second Fort could not have been carried out.

As built, the fortification was apparently intended to measure 490 feet along each front (the line from the point of the top of the parapet of one salient to the next), although the actual measurements range from 483 to 503 feet as a result of various errors. The principal errors in the layout seems to have been a 1 degree error in setting out the central angle (east-west angle is 91 degrees), and a mistake in measurement that added 20 feet to the southwest corner. Each corner should have been 346.5 feet out a diagonal, but the southwest vertex was set at 366.5 feet instead.

Setting the point for the face angles of the bastion worked fine, except that the midpoints were measured along the fronts only from the northwest and southeast angles, offsetting them somewhat because of the earlier errors. The distance of 1/8 of the front (61.25 feet) was then measured perpendicular to these assumed midpoints of the front, and lines marked on the ground along the lines from the salients to these points. The construction crew would then have measured a distance of 1/3 of the front, or 163.33 feet, along these lines from each salient. The point arrived at by this measurement was the location of the outer corner of each flank, and the section of line between the salient and the corner of the flank was called the face. The line from this point at right angles to the face line from the next salient formed the flank itself. At some point early in the construction of the earthwork, but too far along to start over, it was realized that a severe error had been made in the layout, so that when the flanks were marked in their correct positions on the ground, the distance between each two facing flanks was about 160 feet. As a result, the midpoints were about 80 feet from the flanks, rather than the absolute minimum of 90 feet. This meant that the cannon could not be depressed far enough to bear on the area at the center of each front.

The actual minimum size of such an earthwork is 600 feet along each face. The earthwork actually began with an outline of 630 feet on a side, a comfortable size, but this was then used as the outer edge of the ditch, rather than as the crest of the parapet. Grover's basic mistake, worse than the ones mentioned above concerning the layout of the original square, was a simple error at the very beginning of the drawing of the plan for the earthwork. Essentially, he plotted the basic outline of the fort with faces of 630 feet, but instead of marking the ditch outward from this line, making it the outline of the parapets, he measured the ditch inward, making it the outer edge of the ditch. Grover, as the designer, probably made the decision to attempt to correct this fault by making each of the distances from flank to midpoint 100 feet. He did so by reducing each face to a length of 50 feet, and making the curtain (the line of parapet between the inner corners of the flanks) 195 feet long. When this correction was carried out on the ground, across the irregularities of the already-existing ditches and embankments, it was marked out very badly, so that most of the angles and distances are off in varying amounts. This produced the plan of the earthwork as it stands today. The fortification was declared capable of maintaining a defense as of August 26, 1861, although it underwent almost continuous further construction work through early 1863.

Apparently everyone involved in the effort to construct the fort kept quiet about the mistake; had it been known outside the very few persons directly involved in the work, it would have been loudly discussed in the same article in the Santa Fe Republican, July 5, 1862, that scathingly made public the other errors in its construction: it was too close to the western ridge to be safe from fire directed from its top, and the tunnel intended to supply water to the garrison collapsed soon after construction and was a wasted effort, anyway, since wells begun inside the earthwork immediately found water after the completion and collapse of the tunnel.

However, Grover wasn't through with making mistakes. Not only the sloppy revision of the flanks and faces, but also the need to place the enlisted barracks and the storerooms in the redans resulted from the size error. In fact, Major Chapman himself said on August 26 that the earthwork was "not as capacious as it might have been under other circumstances, but considering the time at which it was commenced, the necessity for its rapid completion and the force to be employed upon it, we have accomplished more than I expected . . ." (Arrott Collection, card 63, Major William Chapman, commanding, Fort Union, to Colonel E. R. S. Canby, Headquarters, Department of New Mexico, Santa Fe, August 26, 1861). Had the earthwork been built to the correct size, there would have been enough room within the parapets for the barracks and storerooms. By September 3, Colonel Canby had become insistent that the stores be gotten into secure, protected storage spaces immediately. The reduced interior space of the earthwork meant that some alternative had to be found for these structures. The earthwork was protected by the usual outworks in the form of earthen banks called redans or demi-lunes; about the first week of September, 1861, Captain Grover suggested that they be altered to contain the Company Quarters, storerooms, and presumably the Officer's Quarters. Grover apparently prepared the design about September 5, 1861, and Lt. Col. Chapman forwarded it to Colonel Edward Canby, who approved it on September 19, 1861 (Canby discussed this sequence of events in a letter from Headquarters, Department of New Mexico, Santa Fe, to the Adjutant General of the Army, Washington, D. C., dated July 22, 1862; the letter of approval is Canby, Headquarters, Department of New Mexico, Santa Fe, to Lt. Col. Chapman, commanding, Fort Union, September 19, 1861; Part I, p. 44; Oliva, "Frontier Army," p. 460). Construction on the barracks and storehouses in the redans was virtually complete by October 20, 1861 (Part I, p. 44). By January 7, 1862, virtually all of the Quartermaster property, Ordnance stores, and provisions had been moved from First Fort to Second Fort.

Unfortunately, once again Grover had miscalculated. Lt. Alexander Robb, who inspected the earthworks in June, 1862, noted that the change to the outworks interfered with the lines of fire from the main earthwork, clearly because they stood too high above the ground; the main guns could not be depressed below a certain angle, or they would fire into the back sides of the barracks. The barracks therefore provided cover to potential attackers.

To sum it up, this is without a doubt one of the most poorly planned and constructed earthworks ever built: an error in the original plan made it too small, the attempts to correct the small size resulted in a poor plan of fire and outworks that provided cover for the enemy rather than the defenders, and the site was chosen too close to superior ground for the defense to be effective even if the design had been correct. It is an obvious case of too much haste and too little experience.

Construction on the fort was stopped on June 12, 1862. The work was under the direction of Captain John McFerran at the time; McFerran designed Third Fort later that same year. However, in November, 1862, a second major effort of building began, resulting in the construction of bombproof barracks, officer's quarters, and a magazine within the earthwork, apparently replacing non-bombproof structures of similar use (Part I, p. 54). In March, 1867, an order came through to demolish the remaining buildings of the second fort and salvage the materials, except for those still being used as laundresses housing and stables, awaiting the completion of HS-16, 23, and HS-18, 26, about 1868. Some were still in use for storage during the late fall, 1867.

Graphic Representations:

Although no maps of the Second Fort as it was designed or completed are available, one plan drawn by Lambert under the command of Captain Henry Inman in January, 1867, shows a sketchy outline of the eastern third of the ditches and outworks. The 1866 and 1868 maps show a rough plan of the Fort, although these maps depict the buildings on its interior as two rows of three structures, with no resemblance to the layout visible in photographs taken in ca. September, 1865, or to the traces visible today. It is possible that the layout of buildings inside the earthwork as depicted on the 1866 and 1868 maps were taken from the original plans of the fortification, and show the layout of the original, non-bombproof interior structures, before the reconstruction beginning in November, 1862. The photographs, 111-SC-88000, 88001 (FOUN 905), and 88004 (FOUN 906), National Archives, were all taken about the same time in ca. September, 1865, probably by Farnsworth as part of his documentation of the conditions at the time.


HSName and Use

Second Fort. This number applies to the entire circumference of the ditches and embankments. By early August, 1861, 200 men were working on each four-hour shift, and it was expected that by mid-August it would be capable of defense (Arrott, card 62). The basic construction was complete by the end of August, 1861 (Arrott, card 63). The original layout of buildings on the interior of the earthwork may have been two rows of three structures, as shown (erroneously) on the 1866 and 1868 maps. These structures were not bombproof, and were replaced in November and December, 1862, with bombproof buildings in a cross-shaped layout, as shown on the present plan.

By February, 1862, it was planned that the cannon would be set in place beginning in May (Rocky Mountain News, March 18, 1862). It is possible that Colonel Paul mined the defenses and warehouses (Oliva, "Frontier Army," p. 487 n. 178). By June, 1862, the problems with drainage began forcing the removal of most of the stores and many of the men from the buildings. Both the North and the South believed that Fort Union was unassailable (Oliva, "Frontier Army," pp. 477, 480) until June, 1862, when Captain P. W. L. Plympton, 7th Infantry, commander of the fort at the time, found that the fort was within range of a 12-pound howitzer fired from the crest of the ridge to the west of First Fort (Oliva, "Frontier Army," p. 477). Plympton referred to the Second Fort as being of "peculiar construction," mentioning the placing of barracks and storerooms in the redans, which Plympton referred to as demi-lunes (Arrott, cards 80, 81). In spite of the problems with the fort, in August, 1862, preparations were being made to place 14 pieces of artillery in the earthwork (Part I, p. 43). By December, 1862, ten 12-pound cannon had been placed in the fort, and "several" guns of larger calibre were being mounted (Mesilla Times, Dec. 12, 1862).

An inspection of the fort during the summer of 1862 noted that the fortification was not completed by that time. The parapet that formed the breastwork was washing away and filling up the ditch around the earthwork. Also, the lack of ventilation and interior moisture were causing serious problems. However, a major new construction effort was begun in November, 1862. For example, additional abatis were put in place on the fortification by December, 1862, and bombproof magazines and barracks were constructed in late 1862 and early 1863 (see HS-209, 210, 211, below).


Redan or Demilune. Officers' Quarters. Designed about the first week of September, 1861, and completed by October 20, 1861. Of the eight redans intended to house officer's quarters, only HS-201 and 202 appear to have been finished, based on the appearance on the ground and Robb's description on June 30, 1862. Robb stated that both of the completed and occupied quarters had the same measurements. They were made up of a series of eight rooms each 16 feet across but of varying lengths. The eight rooms formed two wings meeting at an angle, says Robb; one side of the angle was made up of three rooms, two of them 18 feet long and the third 12 feet long. The other wing is formed by five rooms, 14 feet, 14 feet, 12 feet, 8 feet, and 16 feet. Presumably the 16 x 16 foot room formed the apex of the angle; if so, the two rows of rooms were 64 feet long from apex to end. These quarters had board floors.

The remains of HS-201 on the ground consist of a number of fragments of rubble stone wall with occasional sections of brick. Not enough of the structure is visible above ground to work out the actual plan or to see any correspondence between Robb's description and the physical remains. The appearance of the structural traces, however, suggest that a large proportion of the building remains relatively undisturbed in the ground; archeological investigation would probably quickly reveal the details of the plan and individual room uses.

Either these quarters or those of HS-202 were used as the Commanding Officer's quarters from November 25, 1864, when HS-224 burned, through October, 1866, when Commanding Officer's Quarters HS-5 were completed. Brigadier General Kit Carson was Commanding Officer during most of this period, December 24, 1865 to April 27, 1866 (Oliva, "Frontier Army," p. 565). It is likely that HS-201 was the Commanding Officer's Quarters; its remains are more substantial, suggesting that it may have been maintained better and longer.


Redan or Demilune. Officers' Quarters (see HS-201).


Redan or Demilune. Officers' Quarters, incomplete. This redan is shown on the 1866 and 1868 maps, and is visible on the ground, but no traces of structural remains can be found. It may not have gotten beyond the excavation of foundation trenches.


Redan or Demilune. Company Quarters and storeroom. Designed about the first week of September, 1861. Construction of the buildings themselves largely finished by October 20. By December 15, 1861, the structures were finished and the ditches on their exteriors were being excavated. The dirt was thrown up against the outside and top of the building (Oliva, "Frontier Army," p. 475). Lieutenant Alexander Robb described these quarters as well as the Officer's Quarters on June 30, 1862. He said that the redans housing the Company Quarters were each composed of two wings; each wing was 200 feet long and 26 feet wide. Each was divided into a storehouse 100 feet long, and quarters for a single company made up of six rooms. Allowing for the thickness of the partition walls, each Quarters room would therefore be 15-1/2 feet by 26 feet. They had packed-earth floors, rather than the board floors of the Officer's Quarters.

Inspecting the earthworks quickly revealed the general plan of these buildings on the ground. The Company Quarters were located on the ends of the redans closest to the fieldwork, and had a fireplace on every other wall; that is, each hearth served the two rooms on either side of it. These fireplaces fell at intervals of 31 feet. The chimneys of these fireplaces can be seen in the photographs of the redans taken in 1865, with small air circulation stacks next to them along the tops of the earth-covered buildings, one to each room. The ditches on the outside of each building are largely silted up, but seem to have been about 17 feet wide. The curved portion of the apex of each redan was apparently solid earth. As with the Officer's Quarters, considerably more detail about the construction of these buildings, as well as the use of the various spaces, could be recovered by a careful archeological investigation.

As new company quarters were completed in Third Fort, men were moved out of the Second Fort barracks. Marian Russell lived in one of the Company Quarters for a time in 1864 (Oliva, "Frontier Army," p. 757). By November, 1866, it was reported that no enlisted men remained in the barracks at the earthworks (Oliva, "Frontier Army," p. 575). After abandonment, the buildings were used as laundresses quarters from about November, 1866 to late 1867 (Oliva, "Frontier Army," p. 594; Part I, p. 57), when the laundresses were moved into their new quarters along the west side of the Post Corral.


Redan or Demilune. Company Quarters and storeroom. Two of the barracks were converted to temporary stables beginning on November 21, 1866; the Lambert and Inman map of January, 1867, shows that one of these stables was in the eastern half of this redan. The other was probably in the west half. The use of these barracks as stables continued until completion of the Post Corral stables in late 1867.


Redan or Demilune. Company Quarters and storeroom.


Redan or Demilune. Company Quarters and storeroom.


Headquarters Offices? Probably designed and built as part of the major reconstruction of November, 1862. This building has very sharp edges and flat sides, and was apparently built with an exterior casing of wood or stone. The featureless appearance suggests stone as the more likely material. A thick layer of earth forms a cap on the building. A single large ventilator is visible at about the center of the cap in the ca. September, 1865, photographs. The flagstaff, HS-225, for the Second Fort stood just north of this structure, probably in front of the main entrance.


Company Quarters. Two of these structures are mentioned in an article in the Denver Rocky Mountain News of February 24, 1862, and described by Lt. Robb on June 30, 1862; he says that they were constructed inside the works but were only temporary, and would have to be rebuilt to be permanent. Both of these were rebuilt as bombproof barracks during the reconstruction of November-December, 1862; orders requiring this were sent to Fort Union on December 20, 1862 (Part I, p. 54), indicating that the work probably occurred in late 1862; however, a week earlier, on December 12, 1862, the Mesilla Times described the Magazine (HS-211), quarters (HS-209, 210, and 212) and "all the garrison buildings" to be bombproofs already.

The ca. September, 1865, photographs shows some details of this structure. Five ventilators or chimneys can be seen, one at each corner of the roof, and one in the center. The main entrance to the structure was a doorway at the south end near the southeast corner; this is rather poorly placed, since it faces the opening of the main gate of Second Fort, making it possible for a shot to pass over the traverse covering the entrance and penetrate this doorway. The north end of the building seems to have been built against the Headquarters building, HS-208.

After the abandonment of Second Fort, HS-209 was dug out and most of its useable material salvaged, leaving a large oval pit.


Company Quarters. These Quarters were probably also built as a bombproof building in November-December, 1862. The ca. September, 1865, photographs shows some details of the building. It had two doors, one on the south face at the west end, the other on the east end near the northeastern corner. Six small loopholes or tiny windows are spaced evenly along the south side. Five ventilators can be seen on the roof, two at the west end, two at the east, and one in the center; all seem to be offset somewhat towards the south edge of the roof. No chimneys can be made out in the photograph, but various odd marks on the roof could be partly demolished chimneys.

This building appears not to have been dug out for salvage; it is possible that the structure collapsed in place. If so, a great deal of structural information waits to be found by archeological investigation.


Magazine. Plans for a bombproof magazine within Second Fort were discussed on November 26, 1862. Captain Shoemaker suggested that the building should be about 60 feet long and 25 feet wide, excavated 8 feet into the ground and walled with upright timbers faced with rough boards. The wall timbers were to be 14 feet high, with the roof beams of horizontal timbers resting on the side walls and supported in the center. The beams would slope downwards from the centerline towards the walls, and would be covered with boards and at least 3 feet of earth. A door was to be placed at each end, and a board floor built of planks on joists. This magazine was begun in late November, 1862, and completed in December (Part I, pp. 52-53, 54; Oliva, "Frontier Army," p. 548-49). It was still in use for vegetable storage for the Post Commissary in October, 1867 (Oliva, "Frontier Army," p. 590).


Officers' Quarters. According to 1st Lt. Alex W. Robb, June 30, 1862, one officer's quarters with four rooms stood in Second Fort by the time of his inspection, but was apparently not a bombproof structure. However, it was rebuilt as one in late 1862, probably at the same time as the two barracks and the magazine (HS-209, 210, and 211) were built in November and December, 1862. The ca. September, 1865, photographs shows the building as a bombproof with two chimneys, one on the north and one on the south center of the roof, and a ventilator on the east side.


Well. A well was under construction within the earthworks by early January, 1862, apparently begun after the collapse of the water supply tunnel (HS-222) in late 1861. Eventually, three wells appear to have been dug. HS-213 and HS-214 were inside the parapets themselves.




Well? Unlike the two wells above, this circular structure is located in one of the redans. It is possible that this is not a well; however, no suggestion of any other structure is available.


Traverse? This structure, of packed earth, was designed to prevent incoming fire from passing through the gap in the parapet formed by the main gate.


Possible Traverse?


Workshops, Offices, and Temporary Storehouses. Probably built in August and September, 1861 (Part I, p. 44). This is actually a series of several buildings in a row, as can be seen in the ca. September, 1865, photographs. At least seven or eight chimneys are visible in these photographs, several of them producing smoke. The first building on the northwest end appears to be made of canvas on a wooden frame. At its southeast end is a large rectangular object standing well above its gabled roof; this looks like a large chimney. Next is a low structure, apparently of wood, with a shed roof of shallow slope. A small chimney appears at its southeast end. At its north end, obscuring the point where it contacts the canvas building, is a small room extending north at right angles to the main line of the series of buildings. This room is made of horizontal logs, and has a flat roof. Southeast of the shed-roofed building is a long building with four or five chimneys and a gable roof. At least one other chimney is producing smoke past the visible end of the long building, but no further details can be seen.


Workshops and Offices. No clear traces of this building can be seen on the ground. It is known to exist only from its presence on the 1866 and 1868 maps, and because two photographs of Second Fort were taken from the top of some structure in this location in 1865.


Embrasured Gun Batteries. These guns fired through embrasures, or slots in the parapet, located on the faces, flanks and curtains of the fort. There are 24 of the platforms for these batteries; at least three can be seen in the ca. September, 1865, photographs; the straight line of the wooden platform is easily recognized in the pictures. At least seven embrasures can also be seen cutting the parapets of the fort.


Gun Batteries en barbette. These batteries are somewhat conjectural, pending archeology. Four positions for guns firing over the parapet, rather than through an embrasure, at the salients (the points of the bastions) of the fort. Unfortunately, none of the salients are visible in the 1866 photographs. The western bastion contained a 6-pound gun in June, 1862 (Arrott, card 81); whether this was at the salient is unknown. For purposes of comparison, see the plan of the Confederate star fort built at Arkansas Post, built in 1862; Roger E. Coleman, The Arkansas Post Story: Arkansas Post National Memorial, Southwest Cultural Resources Center, Professional Papers no. 12 (Santa Fe: National Park Service, 1987), p. 105, fig. 33. This fort had several guns set up en barbette, one of them at the southeast salient; the other eleven gun positions were apparently embrasured, including those in the other three salients. See also the plan of fortifications at the mouth of the Rio Grande, "map of the North End of Brazos Island," prepared in 1865 by Captain D. C. Han, Army Engineers, in the collection of Palo Alto Battlefield National Historic Site, Texas. This map shows the specifics of an octagonal fortification including a plan of its gun platforms and a cross-section of the platforms and parapets, with construction details. The specifics of the barbette and embrasured guns shown on this plan match those reconstructed from the surviving traces of the Fort Union fortification quite closely.


Tunnel. This was a tunnel for getting water from a cistern near the bank of Coyote, (or Wolf) Creek, rather than an "escape route," as most of the speculation about it seems to assume. A brief description of the tunnel appears in the Santa Fe Republican, July 5, 1862, p. 1, "Fort Building in New Mexico." The article indicates that the tunnel had been built in 1861 as a means of insuring a water supply for the fort. Soon after being finished, part of the tunnel collapsed; about the same time, in December, 1861 or early January, 1862, wells dug in the fortifications reached water (Arrott card 72, Oliva, "Frontier Army," pp. 394-95; see also HS-213, 214, 216), giving a better source for the needs of the garrison and making the tunnel unnecessary. The tunnel was lined with boards and was about 3 to 3-1/2 feet in width. It was about 4 feet high, roofed with planks, and had earthen sides shored with boards every few feet (Part I, p. 58). It appears to have begun in the outer slope of the south ditch, under the entrance bridge (HS-223, below). It ran southwest from the Star Fort for about 950 feet, apparently to a covered cistern about 100 feet from the present creek bank. The last 250 feet before reaching the cistern shows a wider and deeper depression, along which can be found board fragments, suggesting that this part of the tunnel may have been the area of collapse; or it may have been dug out. The rest of the length probably preserves much of the tunnel structure intact.


Bridge. The 1866 map shows some sort of narrow crossing of the south ditch of Second Fort, giving access to the main entrance through the parapet. On the ground, this appears as a short stub of an earthen ramp extending about 30 feet from the south side of the ditch towards the main entrance. The remaining 35 feet had no such ramp; the floor of the ditch continued across this area unbroken. However, several mounds of large cobbles and small boulders seem to have a certain symmetry to their location. When plotted, the evidence indicates that the inner 35 feet of the entrance ramp was of wood, supported on massive posts partially protected by mounds of stone. Provision was probably made to raise or destroy some part of, or all of this bridge, in time of attack.


Commanding Officers' Quarters, Second Fort. In February, 1863, an order came through to salvage building materials from the Sumner House at First Fort and constructed a new temporary officer's quarters near the fieldwork of Second Fort. The choice of site was left up to the discretion of the commanding officer. The building was supposed to be a temporary log building plastered on the interior "with blinds for the windows and a gallery running along its front, say ten feet broad." The building was supposed to have a roof of lumber and chimneys of stone. These quarters were occupied by April, 1863 (Part I, pp. 38-39, 54-55). HS-224 appears to be the Commanding Officer's Quarters that burned on November 25, 1864, completely destroying the building and apparently forcing the commander to move to one of the officer's quarters in the redans, probably HS-201 (Oliva, "Frontier Army," p. 540).

The arroyo has cut into the southeast corner of the structural remains, but still a good deal of scattered fieldstone and trash are easily seen. At least two areas that appear to be the remains of chimney bases are identifiable.


Flagstaff, Second Fort. Approximate location. The photographs of ca. September, 1865, show the flagstaff standing just north of the Headquarters building, HS-208, on the centerline of the fort and apparently centered between the Headquarters building and the Magazine, HS-211, just to the north; it was probably in front of the main entrance to the Headquarters building. Probably erected in June, 1862, and a request for a garrison flag submitted to Headquarters, Santa Fe, on June 27. Still standing with a flag flying in ca. September, 1865. Archeological excavation would probably confirm the exact location of the flagstaff.

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Last Updated: 13-Feb-2006