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ARCHAEOLOGICAL INVESTIGATIONS AT
FORT BONNEVILLE


by
David Vlcek, Bureau of Land Management

A Paper Presented at the Rocky Mountain Fur Trade Symposium
September 10-12, 1992, Pinedale, Wyoming

The Fort Bonneville Site (48SU29) is an historic period settlement established in 1832 by Captain Benjamin Louis E. de Bonneville on the banks of the Green River in present-day Sublette County, Wyoming. The site occupies a dry terrace of the Green River just above its confluence with Prairie Creek, five miles above the Green's confluence with Horse Creek. Fort Bonneville, sometimes called Fort Nonsense due to the severe winters noted for the site environs, was intermittently occupied from 1832 to 1836. Ft. Bonneville is the first historic period building locale known for Wyoming and is listed on the National Register of Historic Places.

In 1989, the Sublette County Historic Preservation Commission developed and supervised a research project at the site as part of Wyoming's Centennial celebration. The project involved use of nondestructive archaeological discovery techniques as well as conventional small scale test excavations. Conventional aerial photography was done, infrared aerial photography was attempted, and portions of the site were surveyed using a magnetometer. This latter technique was judged to be most appropriate because of the presumed presence of metal artifacts within the site that should express themselves strongly as anomalies on the color printout generated by magnetometer surveying. Metal detector surveys were repeatedly performed at the site, first to "clean" the site surface of modern metal trash; later to assist in the controlled excavation of test units within the site area. Past work at the site was integrated into our project and several local collections attributed to Ft. Bonneville were examined. Many items deposited at the Museum of the Mountain Man in Pinedale are attributed to Ft. Bonneville.

The project was funded by the Wyoming State Historic Preservation Office with a grant to the Sublette County Historic Preservation Commission (a "Certified Local Government"). Archaeological Services of Western Wyoming College was contracted by the Sublette County CLG to perform the magnetometer survey and the excavations. Dudley Gardner and David Johnson were project directors; others making major volunteer contributions include: myself, Russ Tanner, Ray Lovato, Gary Wilson, Ann Noble, Joe Bollinger and a host of volunteers from the Pinedale, Sublette County and Rock Springs areas. To honor the wishes of an adjacent landowner, we limited our project to the southern half of the known site.

The project had several goals, both historic/archaeological and as a community educational effort. The excavations were preceded by a community training session in basic archaeological techniques. The dig was "open" in that local volunteer effort was not only allowed but encouraged and supervised by professional archaeologists at all times. The project meets a frequently stated goal of this symposium- that of melding "academic" interest in the Fur Trade with a more public, museum or people-oriented audience.

Research goals we proposed include: 1). Assessing the utility of remote sensing/nondestructive archaeological techniques on a historic period site. 2). Evaluating the historic archaeological potential of the site. 3). Examining a sample of the material cultural remains presumed for the site. 4). Delineating the fort's boundaries. 5). Assessing the accuracy of archival and historic information attributed to Ft. Bonneville. The Ft. Bonneville project was one of our contributions to Wyoming's 1990 Centennial celebration.

Our interest in Ft. Bonneville had been piqued by prior site investigations conducted by Dr. Perry W. Jenkins, who surveyed and investigated the site about 1905 when irrigation ditch construction exposed site features. Dr. George Frison conducted test pitting at the site in the 1968. Local artifact hunters have periodically pilfered the site. Little substantive material had been published concerning Ft. Bonneville since Washington Irving had published the popular version of Captain Bonneville's journal in 1837. We did not attempt to probe into suggestions that Capt. Bonneville had come West as a clandestine member of Army Intelligence as Vinton and others suggest. We were interested in the site, not so much the man.

Our efforts at the site began by conducting the aerial photography, magnetometer and site clearing efforts. Based on this work and on-the-ground observations, several test units were selected for excavation. Primary goals included a search for the fort balustrade walls, suspected from Perry's and Frison's work. We placed several test units to investigate magnetometer anomalies and intriguing depressions that appeared to be the fort's north, east and west walls. We were also curious to discover if the fort had a prepared floor, internal features, or other later historic period materials. Was the site single component, dating to the 1830's or would we uncover later occupations overlying Bonneville's early occupational surface? How would the site compare to other historic period sites investigated in southwestern Wyoming, such as the Dug Springs Stage Station or Ft. Bridger? How well were historic period artifacts preserved? We excavated a total of 32 square meters at the site, 16 more than the contract called for.

RESULTS

Our limited excavations were successful in answering most, but not all, of our research questions and goals. The public awareness aspect of the project was a resounding success. We located what we think is the western balustrade wall, the forge/blacksmith area, the site occupation surface, and a possible domestic area. Most of the artifacts recovered were removed from within or immediately on top of a hard packed "floor" that we believe was the living surface of Ft. Bonneville at the time of the site's occupation. The floor may not have been formally prepared; its compactness, easily identified during troweling, seems to have been the result of human use and trampling rather than intentional construction. The floor was found at a depth of from 10 to 30 cm. below the present ground surface, but usually within 20 cm. of PGS. At times we had to exercise caution when removing the surface sod layer, as Fur Trade Era artifacts would adhere to the grass root systems. The Ft. Bonneville cultural component was not deeply buried. It appears that the southeastern portion of the fort is poorly preserved.

Four types of artifacts were recovered during our excavations at the site: Metal, glass, bone and lithic. Additionally, artifacts reportedly removed from Ft. Bonneville and deposited at the Museum of the Mountain Man in Pinedale were examined. Non-provienienced artifacts are assigned to Ft. Bonneville only tentatively. About 600 artifacts were recovered from our excavations; perhaps 300 or so additional items are included in the total Ft. Bonneville artifact assemblage.

Excluding melted glass slag, the most common artifact material type recovered consists of metal, usually iron. 422 iron objects, 24 lead objects and 12 brass objects were excavated by the team in 1989. Unusual objects recovered include eggshell (possibly intrusive), red ocher, leather fragments and wood fragments. The most common single artifact type were metal fasteners. 176 metal fasteners were recovered from our excavations; the Pinedale museum houses several dozen as well. We recovered some 162 nails: 31 hand wrought; 66 cut; one wire (intrusive) and 74 nail fragments were excavated. Functional types include wood fastening nails, horseshoe/muleshoe nails, brads, flatheads and tacks. Many of the nails had their distal ends bent to a right angle. This is called "clinching" and functions to aid in securing the nail in place. Ten bolts, two nuts and two metal washers complete the inventory of metal fastening artifacts from the excavations.

Some twenty-two metal projectile points, or triangular objects thought to be projectile points or preforms were excavated in 1989. These include five stemmed iron projectile points, 16 unstemmed triangular points and a diamond-shaped point. Twenty-one of the twenty-two points recovered were found in the immediate vicinity of the forge/blacksmith shop; one was recovered from the eastern site area in a possible domestic use area.

Guns and gun parts are rumored to have been cached at Ft. Bonneville. Our magnetometer and metal detection surveys did not identify any large metal concentrations on-site. It is doubtful that guns will be recovered from within the fort. The Museum of the Mountain Man has two partial gun barrels that are rumored to have come from Ft. Bonneville, however. One is a large bore flintlock rifle barrel, perhaps cut to a shorter length. The other appears to be a smaller bore percussion cap pistol barrel. Our 1989 controlled excavations did recover eight brass percussion caps, (five of which came from a single excavation unit), a .58 caliber lead ball weighing .61 ounces that appears to have been fired, and an internal fragment of a gun, possibly a bridle. Seven of the eight percussion caps and all of the other firearms artifacts from excavation were associated with the blacksmith area. No gunflints were recovered by our project nor are any currently known from the site.

Other metal artifacts of interest excavated in 1989 include a wagon wrench (while we were photographing this artifact in-situ a visiting rancher said, "I've got one just like it in my barn"), a file, a muleshoe, an iron wagon brace, a metal tinkler, a length of coiled metal rings thought to be a length of chain possibly from a beaver trap, a metal spring fragment, a metal object thought to be a flesher, a key handle, a metal hook, and portions of other tools such as files, wrenches, knives and metal tubing. The metal tubing is curious; it may be part of the actual forge mechanism. Discussions among symposium participants casts doubt on this latter suggestion- the diameter seems to be too small to efficiently provide for the passage of air within the forge. All but seven of the over two hundred metal artifacts we recovered were associated with the blacksmithing area.

The Museum of the Mountain Man has in its collections additional artifacts purported to come from Ft. Bonneville. They have gunparts, including a stock mounting ring and part of a powder flask. Domestic items include a knife, fork (of questionable Fur Trade vintage), spoon and a complete teakettle. The buckle and what is thought to be a Laudanum bottle are reported to be from the Ft. Bonneville area. What I consider to be a most intriguing artifact is also housed at the museum. This is a prehistoric Basalt metate carrying the inscription: T F 1824. Originally reported to be from Ft. Bonneville, the item was apparently found near Daniel, WY a few miles downstream from the fort around 1960 by Slim Lawrence of Jackson, Wy.,.

The Basalt metate is incomplete, but evidences both exterior peripheral shaping and substantial internal abrading of the grinding surface. The three closest natural sources of Basalt include the Natural Corrals area near Superior, Wyoming over 100 miles to the southeast, from the Wind River mountain range twenty five miles to the east (and up) and from Hoback Canyon, 40 miles to the northwest. The T F 1824 inscription, if legitimate, could easily be the initials of Mountain Man Tom Fitzpatrick, known to have been in the area at this early date. If Fitzpatrick carved his initials on this Native American artifact, it becomes a fascinating link between prehistory and early Fur Trade history.

Glass in quantity was recovered from the excavations. Dominating this artifact class is melted glass, glass slag and clinker. Almost nineteen pounds of glass, slag and clinker was recovered, all from the immediate environs of the blacksmith area. Indeed, identification and recovery of quantities of glass slag was a main determining factor in positive identification of blacksmithing activities and presence of a forge at the site (Gardner, Johnson and Vlcek, 1991). Several melted glass spheres containing small holes might possibly be glass beads; however, their similarity to fragments of glass slag cannot be denied.

FEATURES

Two features were identified by our efforts; the blacksmithing area/forge and what we take as the western wall of the fort. The blacksmith area was first identified by local volunteer Joe Bollinger as a surface occurrence of melted glass and fire cracked rock. This area was not covered by the magnetometer survey, lying some meters west of the terminus of the magnetometer block. Initial test pitting immediately encountered concentrations of melted glass, metal tools and other artifacts; quantities of carbonized wood, burned soil and fire cracked rock, predominantly quartzite. In total, eight square meters were excavated around the smithing area. The vast majority of all metal tools recovered, many in various stages of manufacture, were recovered from the blacksmith area.

Chemical analysis of the glass from Ft. Bonneville demonstrates similarities in percentages of iron, iron oxide copper and zinc when compared to similar samples from a blacksmith shop excavated at Fort St. Joseph (1796-1812) in Ontario, Canada (Light and Unglik, 1987; Gardner, Johnson and Vlcek, 1990). Glass slag when used as flux is a byproduct of early nineteenth century metallurgy and can signal either the brazing of two metal artifacts together, or use as a medium for removal of impurities in molten metal. Recovery of quantities of slag, fire cracked rock, metal artifacts in various stages of manufacture, carbonized wood in abundance, metal tubing and a zone of burned soil around Feature One leave little doubt that this is the blacksmithing area within Ft. Bonneville. It is located adjacent to the western wall of the fort, near the southwestern corner of the structure.

Feature Two eluded project investigators for some time. One of our stated goals was to locate the fort's boundary. To accomplish this, we had to first locate the walls. Based on Jenkens' early survey, Frison's unpublished work and observations of linear depressions on-site, we felt we had the eastern wall correctly located. The magnetometer survey and several test pits were concentrated in this area. No wall remains, post holes or other concrete evidence of the fort wall was uncovered in the eastern area, however. Using Washington Irving's published description of the fort size, a 1x2 meter test pit was excavated 80 ft. west of where we thought the eastern wall should have been. A few nails and lack of identification of the fort floor or any indication of a wall discouraged investigators.

Dudley Gardner noticed a faint depression that he felt might be a wall depression and excavated a test pit in this area. He located what he interpreted as a postmold and perhaps an excavated wall trench. Several test pits and archaeologist Ted Hoeffer's talented trowel later, we uncovered clear evidence of the west wall, consisting of a series of post molds located in an excavated wall trench, and finally a wooden wall beam in-situ. Linda Scott Cummings has identified the wall beam as genus Populous, probably cottonwood. This confirms both Jenkens and Frison's earlier accounts and establishes the western boundary of the fort.

OTHER ARTIFACTS


Some 600 grams of bone was recovered by our efforts. Identified species include bison, deer and rabbit. The vast majority of the bone by number was recovered as small burned bone fragments, bone scrap and waste bone quite similar to specimens frequently recovered from prehistoric sites in Wyoming. Concentrations of burned bone occur in the eastern fort areas rather than from the blacksmith zone. This fact, coupled with a general lack of concentration of metal artifacts leads the project investigators to suggest domestic activity in the eastern site area investigated. We also recovered one small chert projectile point fragment and six pieces of lithic debitage.

CONCLUSIONS and INTERPRETATIONS

What did our work at Ft. Bonneville accomplish? We established that Ft. Bonneville contains an intact, quite pristine single component dating to the early nineteenth century. We located the west wall, a blacksmithing area and the fort's living surface. We established that among other things, the blacksmith at Ft. Bonneville was manufacturing metal projectile points, presumably for use as trade items for the Native Americans known to have camped just outside the fort. We established the utility of remote sensing techniques on historic period sites of this type. We also feel that we cast some doubt on published accounts of the fort's size (it may be smaller than the 80 by 80 ft. previously reported).

We discovered that metal is quite well preserved at the site, moreso than at later historic period sites in southwestern Wyoming such as the 1860's Dug Springs Stage Station, Rador Springs (late nineteenth century/early twentieth century) and perhaps Ft. Bridger. Alkalai soils may contribute to the preservation problems of sites located more to the south. The recovery of eight percussion caps but no gun flints demonstrates that Wyoming's Mountain Men were armed with state of the art firearms, as the percussion cap was first developed about 1816 and was slow to be placed into firearms production. Despite provenience problems of artifacts donated to the Museum of the Mountain Man, we have expanded our knowledge of historic period activities at Ft. Bonneville and firmly established the site's outstanding historic archaeological potential. We also were successful in involving the local and regional community through volunteer efforts and the open site concept.

We also may have located a totally new component of the site. An area volunteer has identified a nearby locality where historic period artifacts have been located. In that Rendezvous activities are known to have required considerable space, it is not unlikely that 1830's trappers, Mountain Men and Native Americans would have utilized land adjacent to the fort for their activities. Only our future site investigations will determine if this tantalizing suggestion can be demonstrated empirically.

NEXT

What needs to be done next? We'd like to confirm the identification of the western wall by excavating the existing feature to a corner. A bastion may be located there. We also wish to locate outlying occupation material, features, structures or associated components. We also plan to continue the community outreach/open site aspects of the project.

REFERENCES

1991 Gardner, A. Dudley, David E. Johnson and David Vlcek:
"The Blacksmith Shop at Ft. Bonneville". A paper presented at the 1991 Conference on Historical and Underwater Archaeology, Richmond, Va.

1992 Gardner, A. Dudley, David E. Johnson and David Vlcek:

Archaeological Investigations at Ft. Bonneville Ms. on file with Wyoming State Historic Preservation Office, Laramie; and Sublette County Historic Preservation Commission (a Certified Local Government), Pinedale.


 
Last updated: 01-13-2011