I would say that the DC based fed employees are mostly from around here (metro DC) and a smattering of people that transfer to work within the fed system from other places.
It’s been my experience that the engineers, the science types with a specific professional skill like geology and IT are usually white while the general employees and bureaucrat types that just punch a clock and push paperwork are usually minority.
There are a lot of contractors from up north because this area offers a good representation of the NE but with better weather. You can live much larger on a $50k salary in the DC area than you can anywhere north of the Mason Dixon line.
For the most part, the people I’ve run into from down south are hill staffers that leave after a period of time, active duty stationed at the various facilities and ex-mil types that stay for work.
You think the cost of living in DC area is cheaper than Pittsburgh or Scranton?
$50k goes a lot farther there.