• Type: Smoothbore shell gun
  
• Rarity: Common
• Years of Manufacture: Between 1855 and 1864
• Tube Composition: Cast Iron
• Bore Diameter: 9 inches
• Standard Powder Charge: 13 lbs.
• Projectiles: 90 lb. Shells, 150 lb. Solid Shot
  
• Tube Length: 131 inches
• Tube Weight: 9200 lbs. (4.6 tons)
• Range (at 15°): up to 3,450 yards (1.96 miles)
• No. in North America: 1,185
• Invented By: John A. Dahlgren USN
• US Casting Foundries: Alger, Bellona, Fort Pitt, Seyfert, McManus & Co., Tredegar, and West Point foundries

Throughout the 18th and early 19th century the primary ship to ship weapon were broadside guns firing solid shot. This all changed when the French Navy adopted a design of Col. Henri-Joseph Paixhans for a shell gun of 8.7-inches capable of throwing a 59 lb. shell in a reasonably flat trajectory. The U.S. Navy followed suit adopting the 8-inch, 63 cwt. Paixhans-style shell gun in 1841. Dahlgren was determined to design a new generation of shell gun that would be capable of firing explosive shells at higher velocity and greater range. They would also have the capacity to effectively fire solid shot. The ability to fire sold shot would become increasingly important as armored warships appeared on the scene. All of the Dahlgren shell guns were cast in iron, had a distinctive soda bottle shape and all but two had an elevating screw running through the cascabel. Although some Dahlgren shell guns were tested to failure, no Dahlgren shell gun burst during service, a notable distinction for the time. All of the Dahlgren shell guns in service fired shot, shell, shrapnel, canister, and (with the exception of the XV-inch shell gun) grape-shot.

The IX-inch Dahlgren was the most popular and versatile of Dahlgren Shell guns made. The IX- guns served as broadside armament on larger ships such as the USS Susquehanna, which carried 12 IX-inch Dahlgren guns in broadside mounts in addition to her two pivot guns and the USS Powhatan which carried 10 IX-inch guns in broadside mounts in addition to her 2 XI-inch Dahlgren pivot guns. These broadside guns would normally be mounted on a Marsilly carriage (see illustration). Smaller coastal blockade ships such as the USS Fort Henry and the USS Hunchback mounted IX-inch Dahlgrens on pivot mounts. IX-inch Dahlgrens were used on several river gunboats such as the USS Essex and the USS. Benton. If mounted as either a pivot gun or a broadside gun the IX-inch Dahlgren had a crew of 16 and a “powderman.”

The CSS Virginia had six IX-inch Dahlgren guns. The USS Monitor had two XI-inch Dahlgren guns.