The longest range cannon fired several miles. The great majority of cannon were 10 and 20 pound muzzle loaders called Parrot Rifles with a typical range of about 2 miles (3,000 - 3,500 yards) firing...
The most common Civil War cannon was the 12 pound smoothbore Napoleon. There were also some rifled guns, and a few breechloaders. If the gun has already been fired in the last few minutes the first...
To blow up forts. Ex: Fort Sumter was fired on by a cannon, to stop charges (or at least weaken them, and to force enemies in and out of trenches. However this is a very general question since cannon...