While world-building, I often find myself fretting over doing things "right". Making sure I have the "right" population for a city of a certain size, the "right" number of soldiers in an army, even the "right" number of bakers in a town. Why do I care!? The players will never interact with the bakers, much less conduct a census with the sole purpose of calling out my poor planning... yet, I fret.
It's just who I am. I want things to have a reason. To not be scattered higgledy-piggledy and just poured in without rhyme or reason.
Well, today I want to explore one particular manifestation of this demographical mania, and the system I use to address it. I would like to discuss how I decide where to place a settlement while world-building. Ultimately, the whole system boils down to one question, "why settle there?"
There are several possible answers to this question, but I assume one thing to be true in all cases. People always have a reason to settle down. They rarely just stop in the middle of nowhere, unless they have a reason or several reasons. There are many different reasons a settlement might spring up, and the reasons for a particular settlement can also often shed light on its character.
So, if you are plugging away at a world atlas for your game or novel, giving some consideration as to why a settlement formed can, in turn, help flesh out the tone, denizens and other elements of the location as well.
Here are some of the possible reasons that could lead to the formation of a city.
Nearby resourcesThe necessities of life
With few exceptions, cities tend to spring up near sources of food, water and shelter. In particularly hostile environments, these sources might be rudimentary, like a brackish well in the middle of a desert, but the settlement location should offer more availability than the surrounding area, especially if that area is particularly harsh.
Now, this is not to say that settlements don't spring up in the absence of these things, but to survive, they will need a way to get them. Food and water might need to be transported in, or in a fantasy setting, summoned through a portal to the plane of bacon and water or something.
When placing settlements, look to rivers, oases and lakes as attractive spots. Also, consider what sort of animals or plants can be found in the area, as these may have a significant effect on the culture. Agrarian settlements on plains or grasslands will likely eat more bread, grains and grazing animals, while those in a forest might have more nuts and berries in their diets. That sort of thing.
Aside from the necessities for life, towns often form around valuable resources. Many of the cities and towns around western Washington, where I live started out as lumber or mining camps, or because of access to fishing, or farming resources. If a resource is particularly rare or valuable, in might draw people to climates where they otherwise wouldn't consider settling. Think of the oil and gold rush towns in Alaska, or the natural gas boom-towns starting to spring up in the middle-of-nowhere Dakotas.
Resource-based settlements can be temporary in nature, especially if they are short on other reasons for people to settle. The mountains of the Pacific coast are dotted with ghost towns that were abandoned when the gold rush ended, or coal mines closed up. The more successful and long-lasting resource towns often had multiple resources going, or other reasons to help them flourish.
SafetyMany settlements spring up in locations that offer some form of additional safety. This safety may come in the form of a military establishment like a castle or fort, or in the form of some natural feature that provides shelter from adverse weather, like a bay for protecting ships, or to provide an exotic fantasy example, the Valley of the Wind from Miyazaki's anime, Nausicaa in which the prevailing winds provide shelter from toxic fungal blooms. The settlements on the rocky outcroppings of Arakis in Dune are another example.
The people drawn to safety-based settlements are not always drawn for that reason. Many are drawn to the spot by the other people (I guess this is true for any settlement). A military outpost might be stuck in the middle of nowhere for strategic purposes. The soldiers bring their families. Soon, merchants and other services recognize an opportunity and arrive to provide for the populations' needs, and things expand from there.
It's on the Way to SomewhereSome settlements spring up as part of the natural flow of people from place to place. If you consider the natural rhythm of travel and rest for people on a journey, you'll get some idea of how this could work. Typical folks travel by day and rest by night, so while traveling between two distant spots, they will want to stop for some time about every 8 to 12 hours at the most. If a particular path is traveled by many people, these rest spots make ideal locations for settlements to spring up. Enterprising folks might establish inns, services for repairing vehicles, for resupply, or markets for trade, especially if the location is a crossroads or branching point along trade routes. In a world where travel is by foot or ox cart, every 10 to 20 miles might find a village with accommodations for overnight travelers.
In worlds without high technology, wayside settlements might also spring up near notable landmarks used by travelers to mark their progress. I tried looking at some of the landmarks along the Oregon Trail to use as examples, but while some do have settlements nearby, the towns I looked at were founded for reasons other than the landmark... so, perhaps a landmark, plus nearby resources is the way to go.
It's a Jumping off pointSimilar to settlements on the way to somewhere, jumping off points are places where travelers might gather to prepare before setting off on a particularly long or challenging part of a journey. Port cities are an excellent example of this. People gather as supplies are transferred from overland to sea-born conveyance and back. My hometown, Seattle, really started to take off during the gold rush when miners stopped here to gear up before heading to Alaska.
Jumping off points can often become large settlements as people flow into and stay awhile before leaving. Long journeys require significant preparation, and these settlements will attract folks who can provide supplies, guidance, protection or other services to travelers before they leave.
River crossings, port cities, or the edges of vast deserts or mountain passes all make good locations for jumping off point settlements.
It's Far from AnywhereThis might seem counterintuitive, but under certain circumstances, people might choose to settle in a spot, precisely because it is remote. Religious sects might be drawn to a location where they can practice their beliefs without distraction. The buddhist settlements in Tibet, and the pilgrims' settlement at Plymouth are good examples of this. Remote settlements might also attract those who want to get away from crowded cities, and established government guidelines. Perhaps they are looking to be a big fish in a small pond. Perhaps they want to spread out where land is cheap and plentiful, or perhaps they would rather live where their past is less likely to follow them. We see archetypal examples of all these sorts in the tales of the American West, which often involved settlements far from anywhere.
If you keep these various reasons in mind when picking out a spot for your next fictional city, it can make the process of choosing the perfect location a little easier. It might also help tie the settlement to the rest of your world's history and geography in meaningful ways, and can even help inform the characteristics of the people who call it home.