|November 21, 2002
Volume 33 Number 7
|A publication for the faculty, staff, administrators, and friends of California State University, Chico|
Without Shovel or Trowel
Archaeologists investigate Bidwell Mansion underground without turning soil
Bidwell Mansion State Historic Park is slated for a makeover. Over the next five years, using historical photographs of the mansion grounds as a guide, the California Department of Parks and Recreation (DPR) will phase in a new "historic landscape plan" designed to return the grounds to a turn-of-the-century look. The DPR had every reason to believe that the grounds contain important archaeological features, but their historic resource management policy requires avoidance of impacts to historical features such as traces of old buildings. So, specifying that we not dig, the DPR asked the Archaeological Research Program to help determine where these archaeological traces might be located.
An archaeologist without shovel or trowel? Sounds unusual, but, nowadays, new technology and old-fashioned research methods often take the place of digging implements at the beginning of an investigation.
What secrets might the grounds hold? We focused our efforts on four avenues of inquiry, which we pursued and evaluated as independent lines of historical evidence: (1) documents, (2) photographs, (3) maps, and (4) "remote sensing" technology.
Documents, Photographs, and Maps
The Bidwell Mansion, built between 1865 and 1868, was home to John Bidwell and his wife, Annie Ellicott Kennedy Bidwell, until their deaths in 1900 and 1918, respectively. The mansion and grounds were deeded to the State of California in 1923, which awarded title to then Chico State College. The college used the mansion as a women's dormitory until the postwar period, then converted it to an art building. In 1964, the mansion and grounds were deeded to the state for preservation as a state park and museum to honor the Bidwells' contributions to local history.
Our research revealed that completion of the mansion in 1868 marked the end of the grounds' most active and diverse period of economic activity. The grounds were at the economic nucleus of John Bidwell's 1849 land grant purchase, the operational center of his massive Rancho Chico holdings dedicated to provisioning the population of the growing North State. We found that three important buildings existed on the parcel before the mansion: (1) Bidwell's original log cabin residence built in 1849 (some sources indicate the mansion was built near the footprint of the cabin); (2) the "Old Adobe," a two-story structure built in 1852 and demolished in 1876, which first served as Bidwell's residence and office and later as a hotel and bar; and (3) the "Bidwell Store" or "brick store" built in 1852 and probably demolished in stages between 1872 and 1874.
Bidwell's diary entries, ledgers, maps, and notes are mostly mute about building locations. We encountered no formal civil map of the cabin, adobe, or store, and we found no photo showing the Old Adobe and mansion in the same frame. However, an oblique "bird's-eye" rendering of Chico dated 1871 shows both the Bidwell Mansion and Old Adobe (absent the store), and several period photographs depict the adobe and store prior to construction of the mansion. The oblique view (Figure 1) shows the adobe walls aligned on an east-west bearing with the mansion. An 1854 photo, thought to be the earliest on record, taken from the roof of a two-story building at the approximate current location of First and Main Streets, seems to confirm the location and alignment of the adobe (Figure 2). An 1858 photo looking downstream on Big Chico Creek west across the Tehama Road bridge (Figure 3) shows the store lagging onto the creek bank. The Old Adobe can be seen through the trees to the right, behind a mounted party on Tehama Road.
The final phase of our study was a remote sensing investigation on the mansion grounds using a cesium vapor magnetometer (CVM), an advanced instrument that tracks minute degrees of variation in subsurface electromagnetic fields. Modern CVM applications are also linked to software capable of converting the data into graphical plots that can be further enhanced to help identify archaeological traces.
We were initially concerned that the CVM would be unproductive. Bidwell's diaries indicate that a granary and warehouse built in 1874 across Tehama Road from the mansion was built on a seven-foot-wide, multitiered foundation of adobe bricks "from the old building," presumably the demolished Bidwell Store. An entry on Dec. 14, 1889, indicates that Bidwell's ranch hands were "hauling to fill old adobe hole." These entries, along with biographical notes from Bidwell and his neighbors and acquaintances, indicate that archaeological traces of the original Bidwell buildings could be scattered among other historical structures nearby, so even the building footprints could be difficult to identify. Nevertheless, the CVM sampling grids registered a number of profound subsurface features, and three possible building footprints were identified (Figure 4).
A cluster of traces found near the center of the front lawn was a good match for the location of the Old Adobe. The CVM results indicated no profound features, but a series of small anomalies suggesting the footprint was filled with rubble. A creekside sampling grid registered another small archaeological trace that may be the footing of the original Bidwell Store, agreeing with historical photographs that show the store's south wall perched on the break in slope. A backyard sampling grid produced an interesting anomaly best described as a "textured concourse" three to four feet wide in the form of a half rectangle interrupted on the north side by intrusive modern features. The "concourse" lacks the profound signatures indicative of bulky stones or metal which might register higher electromagnetic fields, but it is consistent with an arrangement of burned earth or adobe which might be expected for the remains of the Bidwell cabin, burned in 1852. If it is the footprint, the building would have measured approximately 35 by 25 feet.
What We Know and Don't Know
Documentary and photographic research indicated that the mansion grounds hold a variety of archaeological remains associated with Bidwell's extensive ranching and farming concerns dating between 1849 to 1868. Our conclusions are provisional because each line of evidence was strong in some areas and weak in others. The historic maps were a disappointment. Documentary and photographic research gave us a partial fix on the location of the Old Adobe and Bidwell Store, but no information on the cabin. The CVM traces were fairly strong for a feature attributable to the log cabin, but weak or fragmentary for the possible locations of the Old Adobe and Bidwell Store.
The DPR has incorporated our results into their management plan and will develop historical landscape features and interpretive facilities at the mansion in a way that avoids impacts to the sensitive locations. However, we cannot escape the "digging" angels of our nature and have recommended that the DPR sponsor further archaeological studies to demonstrate that these locations, in fact, represent historical building traces. We've also pointed out that the possible Bidwell cabin trace west of the mansion overlaps DPR lands and adjoining CSU, Chico campus grounds, and we have suggested that the DPR and CSU, Chico work together to develop a joint management plan for this and other potential shared cultural resources. If this is indeed the original cabin footprint, it would be a potentially significant historical resource.
Greg White, director, Archaeological Research Program
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