Anyway, I came across my old early 90s Blue Guide to NYC, which is the last of the really big, detailed editions of that guide in which they will have pages in small print on the history of obscure buildings. Far, far better than the more recent Blue Guides and the current AIA NYC guide. Get a used one if you're interest in this stuff. I love architectural history so I read these books just for fun, just as I eagerly await "Streetscapes" every Friday in the NYT. The North River is mentioned.
Then, I went to the Wikipedia article referenced by others and went through some of the references. That was fun - all kinds of different stories. My short-term memory is not perfect, but one seemed to say that the Dutch called it the North River to avoid confusion with the Delaware River. Another said that, ironically, Henry Hudson named it the North River. There was an exchange of letters or articles a hundred years ago (300th anniversary of HH's discovery) about whether to extend the name of the Hudson River to the Atlantic to honor Hudson, and whether the northern boundary of NYC was also the dividing line between the North and Hudson rivers. The funniest one is the travel article (I think) from 2002 in which a schooner captain, apparently giving a tour, was asked why he called it the North River and his answer was something like: Because you take the North River to go north, and the East River to go the other way. Hilarious.
I have been living in China for over a decade reading a lot of history and now just spent my first year in Korea - returning to China to visit my old university (job) and then to video some things in North Korea next week. So, I have been studying the history and culture of those two nations (or is it three nations?) in preparation for when I will return to the US next year. So, I am really surprised to find myself reading up on NYC history today...an enjoyable diversion!