Defending the Potomac
By Doug Coleman
DEFENDING THE POTOMAC
On March 8, 1862, Lincoln’s cabinet convened to discuss an emergency. The Confederate ironclad ram Virginia, assisted by boats of the James River squadron, had just handed the naval blockade in Hampton roads an unequivocal disaster, destroying two Union warships, the Cumberland and the Congress, and running another three aground as they fled the monster. Hundreds of Yankee sailors were dead or wounded. What was there to stop the Virginia from steaming up the Potomac to shell Washington? In fact, the Union ironclad Monitor, engaging her the next day. But the point was driven home: Washington and the logistics hub of Alexandria needed river defenses capable of taking on ironclads, both homemade Confederate rams and those under construction for the Confederacy in England and France.
At the time Lincoln became president, the sole river defense was Fort Washington, across the river from Mount Vernon. Garrisoned by a single ordnance sergeant whom the Union commander suspected could be induced to capitulate for a bottle of whiskey, a detachment of marines was promptly dispatched to reinforce this important work. In the war of 1812, the site was occupied by an earthwork called Fort Warburton. When the British sailed up the Potomac in 1814 to burn Washington and ransom Alexandria, the garrison abandoned the work ahead of an anticipated mortar barrage and blew up the magazine without firing a single shot. It was replaced in 1824 by a brick and stone masterpiece, reinforced by an earthwork ravelin water battery equipped with a hot-shot furnace. Impressive as this structure was, it did not mount artillery likely to disable an ironclad. Seacoast artillery prior to the war consisted mostly of 24, 32 and 42 pounder long-barreled smoothbore cannon firing much stiffer charges than field artillery. While dangerous to wooden vessels, an ironclad could shrug these off. Rifled cannon were more of a threat, but the Virginia was not disabled even by multiple hits from 9 and 10 inch Dahlgren smoothbores.
Two 1862 maps drawn by artist Robert Knox Sneden portray an irregular earthwork on Jones Point. His note reflects that this battery mounted 100 pounders, almost certainly Parrott rifles. These guns, backed by a sufficient charge of powder, would be a threat to anything afloat, even an ironclad. Maximum range of a 100 pounder is listed as 3100 yards, which would enfilade almost two miles of the narrow channel downriver. While I have never seen any other reference to this battery, Sneden’s maps are usually very meticulous and I have no doubt that such a battery did exist. A fair inference is that it was a stop-gap measure until better works could be constructed.
And eventually better works were constructed. In 1863 Sneden’s “boot battery” was replaced by Battery Rodgers, an earthwork dug into a 28 foot bluff where Jefferson Street dead-ends onto Jones Point. It was within 600 yards of mid-channel and no vessel with a draft of more than 20 feet could pass it at a distance of more than a half mile – point blank range for its 15 inch Rodman smoothbore and five 200 pounder Parrotts. Tests showed that the 200 pounders could pierce eight inches of armor – the Virginia carried two inches of armor over 24 inches of pine – while the big Rodman’s 400 pound shot had the power to pierce 10 inches of iron at 1000 yards and shatter a ship’s frame. The battery enfiladed the channel for the entire range of its guns – 8000 yards for the Parrotts and 5000 yards for the big Rodman. Serving these guns were two large magazines sunk below ground level and covered with a thick embankment of earth proof against any shell or mortar bomb. Battery Rodgers was dismantled at the conclusion of the war and all traces have disappeared.
On the Maryland side, opposite Belle Haven, Fort Foote rose 100 feet above the river on Rozier’s bluff. Even more powerful than Battery Rodgers, Fort Foote mounted two 15 inch Rodmans and eight 200 pounder Parrotts behind thick parapets and traverses. Its guns could support Fort Washington three miles downriver, while Battery Rodgers was close enough to support Fort Foote. Completed in 1863, the earthworks are well-preserved and still contain two of the big Rodmans, including the one originally at Battery Rodgers.
The redoubts on the hills above Belle Haven could also reach the channel and at least annoy hostile shipping with field artillery and 30 pounder rifles. One of Sneden’s maps of Fort Lyon shows some of its 100 pounders pointed downriver, suggesting that this work intended to engage hostile shipping at long distance as well. On the Maryland side, it is a fair guess that the forts on the heights above the Potomac, while not built as water batteries, could lend a hand in a pinch. In fact, given reasonable notice, one could probably expect a lot of mobile field artillery to be moved to within range of the Potomac’s narrow channel.
These river defenses would have been supplemented with obstructions to block the channel or at least delay attackers long enough to really work them over at close range. In practice, an oncoming ironclad steaming along at five knots would have been engaged as it approached Fort Washington with antiquated seacoast artillery, not sustaining much damage but probably wasting a lot of ammunition on the old brick fort. As it passed Fort Washington, it would have been engaged at long range by the guns of Fort Foote, remaining under fire the whole way. As it neared Fort Foote, it would also be subjected to long-range fire from Battery Rodgers and the works on the hills above Belle Haven. As it passed Fort Foote, the big guns would be punching holes in the armor, knocking plates loose and shattering its wooden frame. If the vessel lived long enough to reach Jones Point, the guns at Battery Rodgers really couldn’t miss. An intruder would remain under continuous fire for the hour it took to steam upriver from Mount Vernon to Alexandria, assuming it stayed afloat and did not run aground or become hung up on an obstruction.
In point of fact, the Confederacy never attempted to reprise the British naval raid on Washington and Alexandria. For good reason – after 1862, it would not have worked.
Sources: John G. Barnard, Report on the Defenses of Washington; National Park Service, Mammoth Guns, http://www.nps.gov/fowa/learn/historyculture/mammoth.htm; National Park Service, Fort Foote, http://www.nps.gov/fofo/learn/historyculture/index.htm
Doug Coleman is an attorney and amateur historian in Alexandria; comments and corrections are welcome at email@example.com.