During the Civil War, sieges were relatively common, and both armies undertook them on occasion. As had been true for several centuries, there were two ways to reduce a fort before launching a final assault with infantry: direct fire with standard artillery to batter the walls down, and indirect fire with mortars to inflict damage on the fort's defenders behind their fortifications. Ideally, the mortars would keep the defenders' heads down while the artillery concentrated fire on one section of the fort or walls, weakening or destroying that section, and knocking out the enemy's artillery with counterbattery fire.
The problem with the latter was accuracy: artillery before the Civil War was rather inaccurate, and even weeks of bombardment could end up with very little damage to the fort's defenders, making the infantry assault a bloodbath. Rifling the barrels was a solution to the accuracy issue, but rifling was very difficult to cast. However, in 1860, Robert Parrott, a former US Army officer, figured out how to efficiently make rifled guns in all calibers. His weapons became known as Parrott guns, and were hugely advantageous to the Union Army--the Confederates, lacking the knowledge of the process or the metallurgy to achieve it, struggled to copy the Parrott design. Though Parrott was better known for his smaller artillery pieces, he also produced several designs for rifled siege guns. These did not get designations from the Union Army, and were just known by the weight of their shot. One of these was the 200-pounder 8-inch siege gun.
The 200-pounder was a scaled up version of the successful Parrott 100-pounder 6.4-inch siege gun, which Union artillerists thought was the finest siege gun of the war. The 6.4-inch was easy to use even for inexperienced artillerists (which could be infantrymen pressed into the role), accurate, and generally reliable, though they burst more often than other Parrott designs, likely due to just the sheer amount of weight they were throwing. The 20-pounders were massive guns by weight, if not by size, weighing in at a hefty 83 tons, with a maximum range of about five miles.
Because of the 200-pounder's weight, they were rarely used in the Civil War--it took too long to arrive, and most armies weren't willing to wait long enough for them to get there. Most of the Parrott siege guns were used in the Siege of Charleston from 1862 to 1865; the most famous was a 200-pounder nicknamed the "Swamp Angel." Engineers under the command of Brigadier General Quincy Gillmore built a wooden platform in a marsh, which Confederate engineers had thought impossible, then emplaced the Swamp Angel on the battery. Gillmore then delivered an ultimatum to the Confederates to evacuate Morris Island or he would fire on the city of Charleston. When the Confederates refused, the Swamp Angel opened fire on August 22, 1863, at a range of just over four miles--at the time, the longest-ranged artillery bombardment in history, and the first to use a compass to aim the gun. The Swamp Angel's bark was worse than its bite, however: though shelling Charleston was impressive, it did little damage to the city or its inhabitants, and the gun burst after its 36th shot in any case, though the crew was unhurt. (A gun believed to be at least part of the Swamp Angel was taken back and is on display in Trenton, New Jersey.)
After the Civil War, the Parrott siege guns remained in service as coastal defense guns for a time--their rifling made them accurate enough to engage ships, and any ship hit by one would sustain catastrophic damage. These were replaced in the 1880s as a result of the Endicott Reforms. A few have survived in museums to the present.
This 200-pounder on display at Fort Stevens State Park near Astoria, Oregon is a replica. It is mounted on the type of wooden barbette that Fort Stevens would have had between the Civil War and the Spanish-American War; Fort Stevens had eight of these weapons arrayed around its various batteries. The gun would be loaded, cranked forward to the end of the wooden carriage, then fired; the recoil would send it backwards to the end of the carriage, where the crew, safely under cover, could reload it. The wooden planks on the ground were arrayed according to preset compass bearings, and the crew could move the gun to bear on targets quickly and easily. This replica can actually fire black powder charges to simulate what the real thing must have sounded like.
