Earlier quoted context omitted.
The area that is now Washington, DC, was not a scene of operations during the Revolutionary War. There were a couple of small port towns, Alexandria and Georgetown, and various farms.
The mosquitoes were probably not averse to crossing county lines to get at that succulent British blue blood.
There wasn't anything particularly important there--capturing Alexandria and Georgetown would have been as effective as capturing Havre de Grace or Port Deposit. And I think that what is now Washington, DC, was part of Prince George's County, which extends east to the Patuxent.