What this island was originally called, I do not know; I'm trying to find out. Back around 1900 it was known as Raz Island, so named for the family that settled there. Then it was sold and renamed Idle Bay Isle by its new owner. Then it became "Riles Island" for a while.
In 1965 Walt Disney purchased the island (and all other land in the vicinity) for the purposes of building Walt Disney World. Ol' Walt called it "Treasure Island", apparently not caring that there was already a very famous Treasure Island in Florida. Disney's Treasure Island opened to the public on April 8, 1974 as a sort of wildlife retreat - but, you know - one of those wildlife retreats where hordes of tourists were allowed to go tromping. The last Dusky seaside sparrow died here in 1987 and was officially declared extinct in 1990.
After achieving classification as a "zoological park", Disney officials made the decision to change the island's name yet again; this time to Discovery Island.
But this didn't last long. For reasons that are still vague and sketchy, Disney abruptly closed the island in 1999 (On April 8, in fact, the same date as its opening in 1974.) But then, weirder still, it continued to operate privately until July 9, 1999, whereupon all the animals were evacuated from the island and moved elsewhere. This has led to rampant speculation about the goings-on here, including concerns about outbreaks of deadly Naegleria fowleri... or something even worse.
Fueling the conspiratorial rumors is the fact that the adjacent attraction, the "Disney's River Country" water park, also mysteriously closed.
According to Modern Day Ruins:
"A boat skipper during a Wishes Cruise told us that the last time Disney folks were on the island removing the last of the useable equipment from the buildings they encountered a gator and a VERY large snake. (He was the boat driver that took them over). The place is now 100% totally abandoned. There was a light that was on during the cruise and I asked about it. He said "notice how it is next to the ground". It was your standard street lamp. It had gotten knocked over during the hurricanes and apparently a wire short circuited and that's why it was on. In my two Ft. Wilderness visits since then, I have not seen the light on any more, so they have now totally cut power to the island."
And so, the question still beckons: why do Disney officials keep this island in a state of abandoned disuse and deterioration? There are still many buildings on the island; you'd think Walt Disney World would have put them to some sort of use.
What do they know that we don't?