How far could the cannon at El Morro shoot?
The size of the cannon determines the range of the shot. The average cannon found in El Morro 200 years ago could shoot a cannon ball a mile covering all of the areas between the forts and across the Bay. Some of the 18 pounders which shot a solid cannonball about 6 inches in diameter had a 3 mile maximum range. This maximum range for the smooth bore cannon is the origin for the 3 miles offshore international limit.