Protecting the Harbor

You’ve probably heard of the Great Wall of China and the Alamo. What do they have in common? They were built to defend people and places. But did you ever think about how their locations were chosen?

The Great Wall of China
The Alamo


Their builders considered the lay of the land and decided on the best place to put them based on geography.

What about Alcatraz? You may know it as a prison, but it was originally a fort designed to protect San Francisco Bay.


And what about Fort McHenry in Maryland? Its job was to protect Baltimore Harbor, which it did successfully in 1812 when the British tried to attack from the Chesapeake Bay.

Fort McHenry


How were the locations of Alcatraz and Fort McHenry chosen based on geography? Bays and harbors often had forts, because many people lived and worked near harbors and bays. Harbor forts are situated so they can control who goes into and comes out of the harbor. If there is a fort on either side of the entrance to a harbor, they can let friendly ships in while keeping enemy ships out. Below you can see San Francisco Bay with a red arrow pointing to Alcatraz.


Below is an aerial view of Hong Kong. It has lots of bays and harbors. Think about where you would put forts if you were trying to protect different parts of the city.


(Photo By Axelspace Corporation –, CC BY-SA 4.0,