Page 22.
At Jones' Point just before crossing Great Hunting Creek, a wide estuary of the Potomac, stands the Light House which marks the spot where was planted the initial stone of the boundaries of the district, which was ten miles square.
The District of Columbia, was authorized by Congress in 1790. The survey of its boundaries was made in 1791. After the completion of the survey the line was cleared of trees to the width of twenty feet on each side of the line. Along this forty foot lane through the woods and over the hills and valleys, stone monuments forty in all, were set exactly one mile apart. They were of free stone, four feet in length, two feet in the earth and two feet above, and on each one of them was the inscription—“Jurisdiction of the United States.” After the lapse of a little more than a century, all but two of these monuments remain in place, but in various states of preservation.
At Jones' Point was also the site of Old Fort Columbia, a fortification of wood and earthwork, mounting some heavy guns, among them the cannon left by Braddock's army in 1755 as too cumbrous to transport over the mountains. This fort was the first attempt by the government to guard the river approaches to the National Capital. It was not dismantled until after the trouble with France in 1798-9. The heavy stones that made the battery, still lie at the end of the point, and some of the guns which made its armament are stuck up as posts at street corners along the river front. Just before this fort was demolished—for it was in 1794 only a ruin—Congress determined to build another one on the Potomac.
John Vermonnet was appointed by Gen. Knox, Secretary of War, in May, 1794, to take control and direction of the new fort, etc., to be built upon the Potomac river. General Washington selected the site for the new fort, a riverside knoll nearly opposite Mount Vernon, and part of the old manor of Warburton, in Maryland. Charles Digges had purchased the land before 1740, and naming it a manor, affected lordly manners. He had his river barge built like a Venetian gondola, and it was manned with negro slaves wearing the costumes of gondoliers. His daughter, Jane Digges, married Col. John Fitzgerald, one of Washington's aides in the Revolution, afterwards Mayor of Alexandria. The land was bought of Thomas A. Digges in 1808 for $3,000, and the new fort was begun in 1809.
Jones Point, Some Old Historic Landmarks of Virginia and Maryland, Described in a Hand-book for the Tourist over the Washington, Alexandria and Mount Vernon Electric Railway, by W. H. Snowden, 1902, pages 22-23. (PDF)
Snowden's illustrations seem to be taken from Marcus Baker's 1897 article in The Records of The Columbia Historical Society, Volume 1, May 11, 1897, Pages 215-224:
