Despite the rich array of perishables Julian Steward (1937) recovered during his 1930s excavations, the Promontory Cave assemblages were dated in relative terms with just a handful of radiocarbon assays until recently. Yet Promontory Caves 1 and 2 are the type sites from which the Promontory Culture was defined, and these assemblages have a critical bearing on our conception of three significant issues in western North American prehistory: the terminal Fremont transition, Numic expansion, and the potential presence of migrating ancestral Apachean populations. To better fix the age of the Promontory Phase, we have undertaken an additional 45 AMS determinations for Promontory perishables. Because of a research focus concerning Promontory footwear, most age estimates come from moccasins, but we have also dated gaming pieces, a bow, an arrow, netting, basketry, matting, and cordage. With the exception of a winnowing basket fragment and some ceramic residue dates, all Promontory Phase assays are tightly focused in an interval running from 662 to 826 radiocarbon years before present (a calibrated 2s range spanning A.D. 1166–1391). Bayesian analyses of the Cave 1 and 2 Promontory Phase perishables suggest that this late period occupation comprised one or two human generations, centering on the interval running from ca. A.D. 1250–1290.