Much of the Northeast has this flavor. I dunno if you've ever been to the Boston area, but many of the buildings have this same sense of history to them. In the leather district, you've got former tanning factories which became porn studios which became software offices and yuppie lofts. In Maynard, you have old textile mills from the industrial revolution, which became DEC in the 50s and 60s, which became Monster.com in the dot-com boom of the 90s, which are now used for web2.0 startups and consultancies. In Lowell, you still see the old textile mills and canals alongside the remnants of the Wang Labs towers and newer businesses.
From what I know of NYC, it's much the same, with bohemian lofts where old tenements once stood.
That's one of the things I miss most about New England, having moved out to California. Here, everything is cookie-cutter suburbia, built in a hurry during the 70s and 80s. There's none of the charm or history of the Boston area. I can walk around downtown Lowell and say "This is a charming city, even if it's a little economically depressed." I can't really say the same about San Jose, even though it's cleaner, safer, and much more well-off.