A large part of the revitalization of economies by war comes from all the rebuilding you have to do *after* them. (This also has the advantage of leaving you with a nice and shiny new modern infrastructure; viz Germany and Japan after WWII, compared to, say, Great Britain and France (which had seen a lot less destruction of their property)).

But, hey, if you'll forgive me for looking at it crassly for a moment: The demand for high-rise office space in NYC just shot up significantly. That ought to bring some stimulation for the building industry in the North-East... And according to standard "Multiplier" theory, it ought to spread from there to the general economy.