Prior to the outbreak of the American Civil War (1861-1865), engineer John Griffen designed a new, all-modern field gun in 3" (76mm) caliber that went on to become one of the best field artillery pieces of the entire conflict. The gun was the muzzle-loaded 3" Ordnance Rifle and utilized a reinforced barrel of wrought iron which limited fracturing of barrels often seen in cast iron types. The weapon became popular with its gunnery crews and a well-respected battlefield piece for its relative light weight-yet-strong construction and long engagement ranges when compared to contemporary smoothbore types of similar form and function. Once it became available in the numbers required, Federal gunnery crews could outrange their Confederate counterparts with lethality by way of firepower and accuracy.
A prototype, known then as the "Griffen Gun" after its creator, was showcased in 1854 and over the next several years the design was improved in subtle ways. Griffen applied for a patent covering the iron construction method for the gun in December of 1855. It was then tested at Fort Monroe in Virginia by the U.S. Ordnance Department - and found to be both reliable and accurate - but not ordered in number until the war seemed all but certain. In February of 1861, the first batch order for the Griffen Gun was placed and another agreement was signed in July of that year.
Its outward appearance was consistent with the times: A heavily-spoked, two-wheeled carriage was used (towed by horse or other beast-of-burden) that included both gun tube and mounting hardware as well as the tow arm. The gun tube was a slender, unbroken single piece of iron made up of layers of wrought iron rods surrounding a cylindrical iron spindle. The spindle was drilled out and rifled, the rifling helping to increase ranged accuracy considerably - up to 1,900 yards depending on ammunition used. The result was a reliable gun tube that was less prone to fracturing yet lighter than competing designs of the period - indeed the overall piece was light enough for gunnery crews to reposition the gun without too much effort.
Over 1,000 of these guns were made for the war effort by the North and most of the lot came from the Phoenix Iron Company of Phoenixville, Pennsylvania. Its accuracy was on full display during the Battle of Atlanta, a major Federal victory, taking place on July 22nd, 1864 in Georgia. Confederate accounts backed the accuracy of the gun in their writings and witness reports and the South respected this new piece enough to attempted to recreate it - though their limited manufacturing capabilities were never able to match its quality resulting in rather poor copies of the original (further hindered by poor quality ammunition).
The guns were also featured in the earlier Battle of Gettysburg of 1863 where nearly half of the Federal guns on hand were 3" Ordnance Rifles. other notable combat exposure included Antietam Fredericksburg.
The 3"Ordnance Rifle managed a long, healthy career in the post-war world, up until the late 1880s at which point more modern breech-loading alternatives of all-steel construction replaced it. It was directly succeeded by the 3.2" Model 1885 rifled field gun (detailed elsewhere on this site) in U.S. Army service and remaining 3" Ordnance Rifles ended their days converted to saluting guns or as breech-loaded 3.2" field guns to help keep them viable battlefield instruments for the foreseeable future.