One of the constants of urbanism and the foundation and growth of cities is that cities are almost always located at or near a water source. The reasons for this are fairly obvious; water is necessary for human survival and irrigation. Most commonly this means cities being founded at a narrow stream crossing or on the bank of a river. Interestingly, however, there are many cities that were started on islands. The most well known cities are those such as Venice and Singapore, that are defined by their nature as island cities. However, other cities also began on islands but have possibly since expanded beyond the physical borders of their beginnings, or only began as cities on parts of larger islands but have since filled the island they are on..
What reasons do some cities have for beginning the core of their settlement on islands, whether they be in the middle of rivers or often just offshore of the a larger mainland. The main reason for this especially in older island cities was usually as an easily defensible location. Islands are much easier to defend as they are completely surrounded by a natural barrier that is difficult to reach with a land army. For instance, the ancient city of Tye in what is now Lebanon was famed for its position as an island city. The city itself was located on an island just off the Lebanese coast, and had survived many sieges in ancient times. Most notable was the siege of the city by Alexander the Great in 332 BCE during his invasion of Persia. As the Phoenicians held naval superiority, Alexander could not attack from the sea. Alexander won the siege through a great feat of engineering and constructed a causeway from the coast out to Tyre and marched his army across. That causeway remains to this day, and the Tyre now sits at the end of a peninsula. With more modern warfare developments such as aerial bombings an island city has become more vulnerable, but for a naval power a city surrounded entirely by water could be a formidable defensive position.
The other major reason why a city might be founded on an island is that it provides a strategic location for trade. This is especially the case if the island the city is built on is at a narrow strait or in the middle of a river. The most successful example of this today is probably Singapore, which has built its success on its position as a city-state in the Straits of Malacca. However, other cities that are not often thought of as island cities also began for this reason as well. Paris, France, for example, originally consisted of just the Ile de la Cite in the middle of the Seine. Even before Julius Caesar expanded the Roman Empire into Gaul, the Parisii tribe frequented the island as a convenient location for crossing the Seine. In 885, Count Odo of Paris warded off a Viking invasion up the River Seine using the island as a great defensive fortification. The Ile de la Cite now is only a minor part of the city of Paris, but it remains a symbolic center of the city as the site of the Cathedral of Notre Dame.
Two other cities across the Atlantic also blossomed as trade hubs, but began as only parts of the islands they are situated on. One of these cities, also founded by the French, is Montreal, Canada. The other is more well known – the island of Manhattan. Both Montreal and Manhattan began on just small sections of their eponymous islands. Montreal started out as a fur trading post founded by explorer Samuel de Champlain in 1611 on the southeastern edge of the Island of Montreal. Likewise, New York City began on the very southern tip of Manhattan in what is today Battery Park. Both cities were advantageous trading locations from the very beginning. Montreal was one of the main settlements on the fur trade from the interior of North America down the Saint Lawrence River. Manhattan grew as a sheltered harbor and as the Dutch and later the English expanded and traded further inland in the Hudson River Valley. Both cities soon exhausted the respective lands on their islands and developed suburbs on the coasts opposite them. Montreal at 1.65 million people is the second largest city in Canada and one of its neighboring cities, Laval, is also situated on an island. New York City is the largest city in the United States, and even if Manhattan was separate, it would still be the fifth largest city in the country at 1.64 million people.
While an island city can be very advantageous, there are also many potential dangers that come with building a large city on an island. As mentioned before, in times of warfare an island, while more defensible, is also more easily blockaded and if the city relies on imports are farming from the mainland for its food, it could be easily blockaded. The more extreme threat to an island city, however, is from the climate and natural disasters. Venice, built on islands in a shallow lagoon, is slowly sinking due to the soft soil of the lagoon, and frequently becomes flooded during unusually high tides. While Italy is currently testing a seawall that should help mitigate tidal flooding in Venice, the sandy soil in the Venetian Lagoon will likely remain a problem. Additionally, while Venice has found a way to hopefully solve its flooding issues, other island cities have not been so lucky. The city of Galveston, Texas, built on a barrier island in the Gulf of Mexico, became one of the busiest ports in the United States in the 19th century rivaling New Orleans, and for much of the century was one of the largest cities in Texas. Sadly, in 1900 a hurricane passed directly over the island and devastated the city. The 1900 Galveston Hurricane is still the deadliest hurricane in United States history. Over 8,000 people or a fifth of Galveston’s population died as a result of the hurricane. The city recovered somewhat, but its golden age was over as nearby Houston quickly overtook Galveston in prominence as Texas’s main port. More recently, climate change and rising sea levels have threatened to engulf some island cities. The most in danger is Male, the capital of the Maldives. Situated in the chain of islands off the southwest coast of India, Male has a population of 153,000 people. However, the highest elevation of Male is just eight feet above sea level, making it one of the cities most threatened by rising sea levels. Potential solutions to rising sea levels are difficult to figure out, especially for a city like Male, and there might not be one. Male and all of the Maldives could have its very existence threatened by climate change in the next century.
Despite these environmental dangers, many cities have been settled on islands throughout history. It is clear that for many island cities, the economic and defensive benefits far outweigh the potential danger of being isolated through disaster or blockade. Some of the greatest economic centers of the modern world including Manhattan and Singapore owe much of their success to their positions on islands and their ability to capture trade from nearby shipping lanes. There are many clear advantages to building a city on an island, and it’s no wonder such a peculiar geographical feature is found in urban centers around the world.