The History Room Committee of the Hudson Area Library presents Dr. Thomas Mounkhall for a two-part multimedia presentation on the Hudson River during two significant time periods. In this presentation, the Hudson Valley from 20,000 BCE through 1500 CE, including migration, macro-change, flora diffusion, contingency and polycentrism. A question and answer session will follow. Light refreshments will be served. Part of the Local History Speaker Series. The second session will be held Sun., Sept. 11. Information at hudsonarealibrary.org or (518) 828-1792 x101.