The Big Eddy Site (23CE426) is an archaeological site located in Cedar County, Missouri, which was first excavated in 1997 and is now threatened due to erosion by the Sac River.

Investigations at the Big Eddy site are quite recent, having been first excavated in 1997, and this area of the state has seen very little previous investigation. The only other extensive study of the region took place in the 1960s and 1970s in the neighboring lower Pomme de Terre Valley (Missouri State University's Center for Archaeological Research (CAR) 2006; Lopinot et al. 1998:39; Ray et al. 1998:73-74). These studies provided a geologic history for the region reaching back some 100,000 years. A long sequence of human occupation was also found, but no evidence of Paleoindian sites.

In the 1970s, with the construction of the Stockton hydroelectric dam, the Sac River, which had for so long preserved the site, began to erode the bank (CAR 2006). This exposed the alluvial layers and began to wash out artifacts from the nearly 14,000 year occupation. Local collectors recovered some of these artifacts, which drew the attention of professional archaeologists. In 1986, the site was finally discovered by professional archaeologists surveying the Sac River valley when they spotted artifacts eroding out of the river bank (Bush 2006; Chandler 2001a; Joiner 2001).

No formal investigation of Big Eddy was conducted until 1997. At this time, the Kansas City District US Army Corps of Engineers came to realize that this site was in imminent danger of destruction by the water releases from the Stockton dam. The Corps hired the Missouri State University's Center for Archaeological Research (CAR) to excavate the site, funding three years of work at the site (Bush 2006; CAR 2006; Joiner 2001).

The CAR team, led by Ray and Lopinot, came to the site with modest expectations. Excavations began with the use of a road grader to remove the plow zone from the site. This material was screened and flotation was used to look for cultural remains (Chandler 2001a). Two test trenches were then dug to a depth of four meters, and four blocks were excavated in 5–10 cm layers to a depth of 2.5 meters. Eighteen deep, continuous sedimentary cores were also taken around the site (Chandler 2001a; Ray et al. 1998:74). This work revealed a much more valuable site than had first been expected and tedious hand excavation techniques were used to investigate the lower levels to maintain contextual information (Chandler 2001a). The 1997 excavations terminated near the base of the Paleoindian deposits at about 3.5 meters below the original surface. Exploratory tests, though, revealed even deeper artifacts, manuports (natural objects moved by human action), and charcoal down to depths of four meters. Dating of these finds were between 12,700 and 13,000 years BP (Ray et al. 2000:68).

After a hiatus during which they examined the previous years' findings, work at the site resumed in the summer of 1999. Hand excavations were made an additional 1.3 meters into the pre-Clovis deposits, finally reaching a paleo-gravel bar (Ray et al. 2000:68-69). It was during these excavations that some of the most exciting discoveries were made, possible pre-Clovis artifacts. If confirmed, these finds could be the oldest in North America. Work ended in 2007.

In total, the US Army Corps of Engineers has now funded five years of excavations, and CAR has returned to the site through the summer of 2006. The team hopes to continue their work through private funding before the river consumes the site.