I think probably it is on leased land, but I don't know for sure. The paper companies that bought the land a century or more ago had a policy of always leasing, rather than selling land. Until a decade or so ago even most of the houses in the center of Millinocket were on leased lands.
Most of the old sporting camps were on leased land, and most of those that have survived remain on leased land, places like Nahmakanta Camps, and chairback mountain camps on Long Lake. Little Lyford POnd camps was on leased land until AMC worked out a deal with the camps owner to buy out the lease. AMC now owns the camps and the surrounding 37,000 acres.
But I know of exceptions. The camps that once sat among the Hermitage Pines were privately owned. About 35 years ago the Nature Conservancy bought the 25 acres and tore the camps down, over my objections. I considered them an important historic artifact. INcidentally, the Hermitage pines are now owned by the National Park Service.
I know this doesn't answer your question, Rick, but if I was a betting person, I'd bet that the land on which White House Landing sits is probably owned by the Nature Conservancy. But I wouldn't wager much money on it.
Weary