In 1938 archaeologist Luther Cressman (from the University of Oregon) excavated at Fort Rock Cave, located in a small volcanic butte approximately half a mile west of the Fort Rock volcanic crater in central Oregon. The Fort Rock Basin is the most northwesterly sub-basin of the Great Basin, Western North America's vast intermontane desert.

 

Cressman found dozens of sandals below a layer of volcanic ash, subsequently determined to come from the eruption of the Mt. Mazama volcano 7500 years ago. Named for the site where they were first found, Fort Rock-style sandals have since been reported from ancient deposits in several Northern Great Basin caves.

Fort Rock sandals are stylistically distinct. They are twined (pairs of weft fibers twisted around warps), and have a flat, close-twined sole, usually with five rope warps. Twining proceeded from the heel to the toe, where the warps were subdivided into finer warps and turned back toward the heel. These fine warps were then open-twined (with spaces between the weft rows) to make a toe flap. Cressman surmised that a tie rope attached to one edge of the sole wrapped around the ankle and fastened to the opposite edge.

Most dated Fort Rock-style sandals are from Fort Rock Cave, but directly dated sandals of this type are also known from Cougar Mountain and Catlow Caves. Directly dated Fort Rock style sandals range in age from at least 10,500 BP to 9200 BP (based on dendrocalibrated radiocarbon ages). For more information, refer to Connolly and Cannon 1999.