I’m just beginning to list sources here. Apologies for not being more complete. I will continue to add to this list as I have time. There are many sources of information on the family named Claessen DeWitt, some better than others.
Record of baptisms and marriages from Kingston, New York.
Ancestors of President Franklin D. Roosevelt
Genealogy of The Hoffman Family, Descendants of Martin Hoffman with Biographical Notes, by Eugene Augustus Hoffman and Ms. Elizabeth Dodds, 1899. Published by Dodd, Mead & Company. Found at: New England Historic Genealogical Society (CS/71/H71/1899), 101 Newbury Street, Boston, MA 02116, 617-536-5740.
Record of early marriages in the Dutch Reform Church in Manhattan, available in printed form or online or online in PDF form.
Record of early baptisms in the Dutch Reform Church in Manhattan, available online
English translations of Dutch colonial records, also known as “The Kingston Papers,” available online. These are the Dingman Versteeg translations. The originals are available on microfilm from the Ulster County archivist, who can be found through the same link. A cross-reference indexing the archive pages to the microfilm frames to the pages in the printed translation can be obtained from Donald Lockhart, dlockhart at rcn dot com, who includes an entertaining introduction about the misadventures of the original manuscript records in the 1800s, before they were at last safely ensconced with the Ulster County archives.
The Hoffman House still stands in present-day Kingston, New York, bought by Nicholas Hoffman in 1707 from Edward Whittaker. Today it is a tavern in Old Kingston, which makes it easy to visit and marvel over.
Genealogy of the Hoffman Family online (see full citation above).
The History of Ulster County, New York
The Oberholtzer Genealogy