HQ is in Armonk which is Westchester County. Somers (since sold) and Poughkeepsie are there as well as is IBM Research at Yoktown Heights. Raleigh is in an industrial park (RTP). I'm by no means familiar with all of IBM's locations but, yes, many of them are suburban. IBM also sold their building in Manhattan in the 90s though they may still have some space there; they did when I last visited but that was quite a while ago. Most of the IBM people I work with work remotely.