The genesis of this was the question about driving to Alaska combined with a few other comments over the years.
Nearly every point in North America that has roads is accessible by road from nearly everywhere else, though having a large SUV, off-road vehicle, etc., may be appropriate for some of them. Anchorage and Fairbanks, Alaska, and the Yukon are connected to the main Canadian road network, which links all eight “mainland” provinces and PEI, and is tied into the network connecting almost everywhere in the 48 contiguous states of the U.S. And this in turn connects with Mexico and that in turn with the Central American nations. (Border crossing problems are not an issue here; we’re talking merely physically drivable connections.)
I noted in that Alaska thread that there was a small road network around Nome, Alaska, connectiong a few outlying settlemetns with Nome, that did not itself connect to any other roads. I indicated I believed there were other examples, and someone noted that only two of the Southeast towns were linked to the Canadian road network, the others having streets in town and perhaps to small outlying areas but without connections to the rest of the North American road network. There were a few other examples from around Alaska as well.
There is a hamlet named Stillwater (one of three of that name) in Herkimer County, New York, which has a small road network to neighboring camps, but the only access to those roads is by boat across the reservoir on which it lies; none of them tie to any other roads.
At one time the roads of Labrador were not connected by land to anywhere else, accessing them from elsewhere being by ferry. I gather, however, that there is now a connection through Gagnon, QC, and Labrador City.
Obviously there will be places like Marthas Vineyard, Catalina Island, and so on, that are only accessible by ferry because of lying on an island.
But I am wondering what other examples there are, if any, of segments of road that are not connected to the main highway grid in North America. I have a hunch the answers may be very interesting from a cultural standpoint.