Rifling came in (in mass use for artillery) in the late 19th Century IIRC - the American Civil War was (I think) the first mass use of rifled artillery in a war.
In the ACW, a large minority of the artillery was rifled. As far as field pieces, the most common was the Parrott rifle. Rifled guns were also common on naval vessles such as the Dahlgren guns and even the Brooke rifles fron the UK. Even though the rifled guns were present, most field commanders preferred the smoothebores as they were already common (less training needed) and were thought to be faster and more reliable.
There isn't a simple answer. The classic 'cannon' in use at the start of the 19th Century were smooth-bored and muzzle-loaded, and fired round shot. Over the next 100 years there were many changes affecting different aspects of artillery, including (but not limited to): - the introduction of rifled barrels (together with elongated projectiles) - the perfection of breech loading mechanisms - the introduction of the metal cartridge case - the development of recoil-absorbing mountings so that the gun stayed on target after each shot - the introduction of smokeless powder for the propellant Plus general improvements in metallurgy and engineering which greatly improved the performance. Lynn is right that the French '75' of 1897 was the first to combine all of the features, most especially the recoil management which enabled a very high rate of accurate fire to be maintained. They were still in use in WW2. Tony Williams: Military gun and ammunition website and discussion forum
I always find it interesting that many of the early Medieval cannon were breech-loading, with a fair rate of fire, but then the world changed to muzzle-loading. There was a good reason, though. The breech-loading was achieved by the 'gun' being a barrel on a frame. The entire 'breech' section (complete with powder & shot) was then slotted onto the end on the barrel, secured in the frame by a few wooden wedges, then after firing lifted out & replaced by the next breech section. This was fine with fairly weak gunpowder (this was before 'corned' powder, you understand), but the system was too weak to allow decent charges of powder to be used. But I digress.