I grew up in the county. The reason it's so well off is the proximity to dc and large tech/defense corridor. The county attracts the rich because you can buy a

I grew up in the county. The reason it's so well off is the proximity to dc and large tech/defense corridor. The county attracts the rich because you can buy a McMansion with land, and still get to work. It's built up heavily in the last thirty years (I passed cow pastures and corn fields on the way to school), but they're mostly gone now.