In the middle of the seventeenth century, the only people living in the American colonies were the Indians, a few scattered pilgrims, and lots of British troops. Communication between Britain and the colonies was confused and chaotic. King George told the troops: "Just pick some kind of headquarters and talk to me from there. I don't care where you put it."
The logical choice for the headquarters was Philadelphia which had a few brick streets and some picturesque supply stores and nobody has ever been able to figure out why the British troops chose Washington instead--which was basically a few shacks in a swamp.
Recently, historians have discovered two facts that might add up to a possible explanation. First, the outskirts of Washington, D.C. lay just a few yards inside the official subtropical zone of the British Empire. Second, all British troops working in subtropical zones were paid time and a half.