General Robert E. Lee, then commanding the Provisional Army and Navy of Virginia, reported to Governor John Letcher on June 15, 1861:

“Arrangements were first made for the establishment of batteries to prevent the ascent of our rivers by hostile vessels. As soon as an examination was made for the selection of sites, their construction was begun, and their armament and defence committed to the Virginia navy.”

The “arrangements” had included a survey of the defensible points of the Potomac by Captain William F. Lynch of the Virginia Navy. In Alexandria, Lt. Col. A. S. Taylor’s Virginia force (two companies) had occupied Alexandria, but was forced to abandon the city on May 5, 1861, and to defend a more tenable position at Springfield. The 1861-1862 Potomac defense line was established under the command of Brigadier General Daniel Ruggles and later Brigadier General Theophilus H. Holmes. This line ran from Mount Vernon in the north to the mouth of the Rappahannock in the south. The Potomac defense line complemented the defense line from Mount Vernon west to Harpers’ Ferry under the command of Colonel (later Brigadier General) Philip St. George Cocke.

(See J. Thomas Scharf, History of the Confederate States Navy.)