The Windy Ridge mega-landslide in Wayne and Sevier Counties originated in Lates tPleistocene time as established by 14C ages on basal organic-rich clay and peat sediment from bogs that developed on the slide. The contact depth between bog and landslide was estimated using high-resolution seismic reflection to find the thickest sediment. Four bogs were cored at their depocenters, and organic material at the slide contact was used for age determinations. The oldest bog sediments ages are 10,600 ± 46, 10,556 ± 34, 12,511 ± 134, and 12,886 ± 91 calibrated years BP. Ages represent two sliding events. First, at the transition from interglacial to younger Dryas glaciation, coeval with the transgression of the Gilbert stand of Lake Bonneville. Younger ages suggest a second slide at ~10,550 cal ka BP. Carbon and nitrogen stable isotopes, and pollen contain a detailed sedimentary record of climate changes since the younger Dryas Chronozone (YDC). The Windy Ridge Mega-Landslide, together with other proxies in the region, provide strong support for a wet period during the transition from late interglacial to glacial conditions at the onset of YDC. Pollen records of this time span are rare in Utah, where local climate variation is complex and illustrates the strength of using landslide bogs as paleoclimate proxies.