Missed this thread when it first started. I live about 35 minutes from the gap, and spend a lot of time up there. I believe I have explored and photographed every one of the abandoned structures from Port Jervis to I-80 on both sides of the river.
The whole story is a very sad one to me, which I won't recount in full here. It's worth some research for anyone interested in Jersey history. It all began with the flood of '55, which killed over 100 people and led to proposals for damming and controlling the last great untamed river in the U.S. In the end Tock Island Dam was never built, and hundreds of families were forced off land they had lived on, in some cases, for over 200 years, often by very crass and extortionate tactics on the part of the Corps ("You don't want to sell? That's your right. It's also our right to remove the power, water, and paved roads leading to your property."). Less than two years after seizure many of the properties were offered for rental while the debate over Tock Island continued. In response to the ads for the rentals placed in the NYT and other papers the whole area was invaded by squatting hippies who took over the structures the families had vacated and stayed for years, until Federal Marshals backed by bulldozers evicted them. It's an amazing story that has gone largely untold.
With respect to the structures themselves, there are plenty that can and should be torn down. These are mostly vacation homes from the early part of the 20th century through to 1950 or so. Virtually none of these are repairable, and few have any historical significance. They've been torn to hell by partying teens in almost every case.
But there are dozens of others that you would really hope can be saved, some of which are pictured in the OP's photos. Most of these have hand-hewn beams which are still fastened with oaken pegs, atop hand-laid stone foundations. Unfortunately every single one of these properties except the official survivor structures in Millbrook has deteriorated dramatically over the last twenty years. The NPS has spent millions on plans and consultants, and very little on roofers, carpenters, and painters. This area encompasses the absolute earliest settlements in Northwestern NJ, including homesteads of the Van Campens, Depuis (Depew, De Puis), and others. The NPS has simply and completely dropped the ball on all of these, and its a damn shame.
The bottom line is that the past cannot be undone. The area is now a park, and the official museum for the structures that used to be there is in Millbrook. Everything else will eventually be torn down or allowed to collapse into a heap through intentional official neglect, with the obvious exception of the "Van Campen Inn" and one or two other structures of historical interest.
