Why were canals built?
Short answer
Canals were built to carry people and goods by boat, bring water to farms, or drain excess water. Their main purpose depended on the place and time.
For example, the Delaware and Hudson Canal in the United States carried coal from mines to markets along the Hudson River.
How it works
Some canals use locks to move boats between sections with different water levels. A lock is a space between two gates, with room for a boat and water. The boat enters, then both gates close. Water flows in or out. The boat floats on the water, so it rises or falls with it. When the water is level with the next section, the other gate can open and the boat can leave. Some canals do not use locks.