"Here were the lots acquired on October 3, 1798 by General George Washington and on which he built two brick dwellings from designs by Dr. William Thornton. A dwelling remodeled from the two dwellings was owned an occupied by Admiral Charles Wilkes, the famous explorer."
A lesser known profession of the General, planter, and president was that of land speculator. His interest in protecting land claimed by the Ohio Company led to a series of events resulting in the French and Indian War. He also invested in land in upstate New York, as did many of his peers in the Virginia gentry.
He seems to have made a wise investment in this case, as you can see from the context of the marker:
The U.S. Capitol is in the background there, about a block away.
Notice also that the marker calls ole George "General." By 1798, the "General" had been out of the presidential office for about 2 years, he had been involved in the negotiations for the site of the federal city, and the city would be inhabited as the capitol 3 years later. So, Washington's wisdom was bolstered a bit by some insider information, wouldn't you think?