Stone tools andmastodon bones occur in an undisturbed geological context at the Page-Ladson site, Florida. Seventy-one radiocarbon ages showthat ∼14,550 calendar years ago (cal yr B.P.), people butchered or scavenged amastodon next to a pond in a bedrock sinkhole within the Aucilla River. This occupation surface was buried by ∼4m of sediment during the late Pleistocenemarine transgression, which also left the site submerged. Sporormiella and other proxy evidence fromthe sediments indicate that hunter-gatherers along the Gulf Coastal Plain coexisted with and utilized megafauna for ∼2000 years before these animals became extinct at ∼12,600 cal yr B.P. Page-Ladson expands our understanding of the earliest colonizers of the Americas and human-megafauna interaction before extinction.