Likely DC, Maryland, Virginia. There is a lot of defense and government contracting in hardware and software in that area. As another person indicated pay is really not that great. I'd add the diversity of opportunity is constrained as well: if you aren't interested in helping the military blow shit up, three-letter agencies probe into private lives, or a handful of NIH- or DOE-funded research projects then you're mainly competing for jobs at much smaller companies, poorly paying jobs at larger companies or pharma labs, or desperately trying to get out.