Key factors driving the late Quaternary extinctions in North America have not been identified. Disagreement prevails over the relative importance of rapid climate change and the apparently synchronous human arrival. This study approaches the question by taking advantage of the abundance of subphreatic megafaunal fossil sites in southeastern New York. An integrated examination of a series of formerly glaciated sites compares pollen and other microfossil data to develop a vegetation and fire history at the local and landscape level. Accelerator dating of animal and plant macrofossils can provide the basis for an absolute timescale in the identification of trends and events in the faunal, vegetational and fire history of the region. Key sites in this analysis include a new mastodon find at Hyde Park dating to 11480±60 and a Cervalces from Pine Island dating to 12180±60 14C yr BP.