Located about forty miles east of Trinidad, the Trinchera Cave Archaeological District is known primarily for its large assortment of well-preserved perishable artifacts, such as basketry and sandals. With diverse occupations ranging from the Paleo-Indian period (before 6000 BCE) to the 1800s CE, the district contains important clues about the process of social and cultural change in southeastern Colorado. The most notable site in the district is Trinchera Cave, which contains eleven rock art panels and has evidence of occupations by at least four different cultures.
The Trichera Cave district includes fifty-three aboriginal sites distributed across 460 acres. In contrast to the dry plains that surround it, the district is located in a canyon system with perennial streams and springs, which would have made it an attractive spot for prehistoric peoples. The oldest artifact discovered at the district dates to the Early Archaic period (6650–3800 BCE), but deeply buried deposits at the Trinchera Cave site itself were recently radiocarbon dated to the Paleo-Indian period. There are also several camps and artifact scatters from the Late Archaic period (1250 BCE–100 CE). Most of the sites and artifacts at Trinchera are attributed to the Developmental period (100–1050 CE), to the Apishapa phase in the Diversification period (1050–1450 CE), and to Plains Apache groups in the Protohistoric period (1450–1725 CE). At least two sites are affiliated with the Sopris phase in the Diversification period.
The Trinchera district was probably used primarily by nomadic groups who maintained brief occupations there, with some longer occupations and farming in the Developmental and Diversification periods. Most of the sites in the district are simple prehistoric camps and lithic scatters (sites of stone-tool manufacturing or repair). At least four of the sites are long-term habitations with extensive artifact scatters and architectural features such as foundations, hearths, and storage cists. The maize, beans, and squash that have been found at some sites could have been grown by prehistoric farmers along the district’s creeks.
Trinchera Cave saw the most use of any site in the district and has the most extensive deposits. A shallow rock shelter in a sandstone cliff, it is more than 200 feet long, fifteen to twenty-five feet deep, and more than fifteen feet tall. Eleven rock art panels line the cave’s walls, some depicting horses. The cave may have been a ceremonial location; one excavation found the remains of a young adult female buried just beneath the surface.
A vast array of artifacts has been recovered from the Trinchera Cave district, including one of the largest collections of perishable materials found in eastern Colorado. Many of these artifacts are now housed at the Louden-Henritze Archaeology Museum at Trinidad State Junior College. The artifacts indicate that inhabitants at the site engaged in wide-ranging networks of exchange with various plains groups to the east as well as with Ancestral Puebloans in the Southwest.
In 1949 Willard Louden first noticed Trinchera Cave during an airplane reconnaissance of the region. Louden soon followed up by taking Jack Gilstrap to the cave for a test excavation. They found a variety of artifacts, including juniper-bark mats and unfired clay figurines. The next year, Trinidad State Junior College archaeologist Haldon Chase also performed excavations at the site. Chase’s successor at Trinidad State, Herbert Dick, conducted further fieldwork at the cave in 1955–57 and reportedly found a large quantity of perishable items, including a possible prehistoric human burial. Little published documentation exists for these early investigations of Trinchera Cave, but Dick gave all the artifacts he recovered to the Trinidad State Laboratory of Archaeology.
In the 1960s the Trinidad chapter of the Colorado Archaeological Society excavated a portion of the cave, but again, little documentation exists for their work. The first well-documented excavations took place in the spring and summer of 1974, when Caryl Wood investigated the previously untouched southwestern end of the cave. She dug five and one-half feet down and found evidence of at least four separate cultural levels. Artifacts included stone projectile points, scrapers and knives, worked bone, ornamental shells, and ceramic sherds as well as corncobs, a yucca sandal, and the remains of deer, antelope, bison, and other mammals. Wood also discovered a bowl-shaped structure with a twelve-foot diameter in the most recent cultural level, with a six-foot fire pit directly beneath it.
More recently, in 1997–99, volunteers in the Program for Avocational Archaeological Certification performed a comprehensive archaeological survey of 646 acres around Trinchera Cave in order to learn surveying and mapping methods. The volunteers produced a new map of Trinchera Cave, documented the cave’s rock art panels, and recorded fifty-seven sites in the district—fifty-three aboriginal, four historical. In addition, from 1999 to 2001 Colorado College archaeologist Michael Nowak took undergraduate field schools to Trinchera Cave, where they found many bone tools, bone beads, and stone artifacts. In 2001 the Trinchera Cave Archaeological District was listed on the National Register of Historic Places.
Finally, in 2013–14 Christian Zier of Centennial Archaeology made a comprehensive map of the Trinchera Cave site, documented the complete excavation history of the site, and reviewed the potential of the extensive collections from the site in the Louden-Henritze Museum. New radiocarbon dating of deep soil samples from the Trinchera Cave collections yielded two Paleo-Indian period dates of 9275–9160 BCE and 8610–8320 BCE, potentially indicating that the flaked stone artifacts found at those soil levels also date to the Paleo-Indian period.
Since the 1870s the Trinchera Cave district has been used primarily for ranching. A wagon road that probably dates to the 1880s and a homestead from the early twentieth century lie within the district’s boundaries. Sheep used to graze the area, and cattle still graze there each winter and spring. These uses have had little effect on the district’s archaeological sites. The top layer of soil in Trinchera Cave has seen extensive looting, but other sites in the area are largely free from vandalism.