Indeed it did have a checkered career, Milson Island.
My late father was a keen fisherman on the Hawkesbury, he and I spent many a time fishing around the island, not all that far from Brooklyn.
There was an old Corvette or the hulk of what was left of it, I always believed it to be the remains of the WW1 ship, HMAS Parramatta.
Just upstream from the island.
Someone told me the bow of the corvette was salvaged and now resides in a park in the city of Parramatta.
I'm going back to when it was a mental institution, reason I heard it was closed was when all that excreta hit the air conditioner over "deep sleep therapy", a-la-one flew over the cuckoos nest electric shock treatment, late sixties?
Dunno how true any of this is, but makes a good yarn.
It, (Milson Island) had a small jetty which at the time was serviced by the "mail boat" which went a fair way up river.
My father told me about the time him and a cupla mates were fishing off the Island and just as the mailman was leaving, an escapee came hooking down the track, ran off the end of the jetty and struck off towards the boat!
Didnt get far, father said, wasnt a good swimmer and soon rounded up!
A braver man than I, that area and around to Berowra Waters well known for sharks!
Dave_64