|From Brno to BQE|
So what happened to Married Island? I can't find any reference to it beyond the account in the History of Queens County cited above and a similar one in Early Long Island: A Colonial Study by Martha Bockee Flint (1896).
It was too small to be what would become Roosevelt Island, that's for sure. U Thant Island, which has its own interesting history, only resulted from the much later construction of "trolley tunnels" to Manhattan. Did it sink into the East River, like a tiny Atlantis? Or did it somehow become incorporated into the Long Island mainland? Or, here's my theory, was it used as a prototype for Myles na gCopaleen's "land migration scheme"?