Mike the Mad Biologist reports on a proposal to do that - back in 1907. Beacon Hill nobs, concerned about the view, put the kibosh on the idea.
If the island had been built, it probably would have languished from the same fate as the Kenmore & West Fenway area. Planned as the next Back Bay and never fully built out to plan because of flight to the new streetcar suburbs.
Chapter six of Karl Haglund's book "Inventing the Charles River" discusses several designs of islands including this one. Fantastic book. A must read for anyone interested in the physical development of our fair city.
Two islands were recently built as part of North Point Park on the Cambridge side opposite Nashua Street Park
If we had the island as drawn, plus 103 years of landscape maturity I think this city would be better for it--but given the odds that this place could've become downtrodden, remodded and modernized ala the west end and many other stretches of the riverfront I'm happy with the safe bet that gives us such an expanse of water
that it was the Bostonians who were worried about the vista. A hundred years later, it's Cambridge that has the stunning riverfront skyline views. Boston has to look at Cambridge, but we get to look at Boston.
I've seen something like that before.
Surely, if they'd built it, we'd be a World Class City now. Is it too late? They could put Menino's Folly there.
If Boston ever starts growing again, it could provide a good zone for the wealthy to build without displacing working class residents of somewhere else.