Before the Industrial Revolution, populations were dispersed across nations. The number of people that could live in a given area was determined by the amount of food that could be produced close enough to the town/village and brought to market before it spoiled. Whether this was through agriculture, fishing, hunting, or livestock, food production was the number one determining factor of a population.

The Industrial Evolution changed that. As I discussed in my post on Agriculture in Gunpowder Fantasy, the reach of farms and farmers, and the ability to mechanize the production process, increased exponentially. This change left many farmhands without work. So they moved to the city, where new textile mills and factories were sprouting up to feed the Industrial machine.

Cities began to grow as more and more people poured into them from the countryside. But immigration wasn’t the only factor in the growth of cities. With better medicine and better food, more people were surviving for longer and having more children. Cities suddenly found themselves growing as much as 50% every 10 years.

On our world, this increase in population was strictly Human. But in a fantasy world, the immigrants and their children could be of a different species. Imagine a world where industrialization has suddenly rendered the majority of a dwarven city unemployed. Unable to feed their families, these dwarves move to the nearby human city, looking for work in the factories, foundries, and mills. They resent the fact that they have been replaced by machines and left to do the most menial tasks.

Imagine the tension between the two species, and any other populations that might live within the city.

This tension could lead to the formation of gangs as young, unemployed citizens roam the streets looking for fun, or to exact their own brand of justice on the world. The seeds of revolution could be planted, driving the nation toward civil war.

Overcrowding would also become a concern, as more and more people poured into the city, or were born into it. A city that had been built to house 10,000, within a generation it finds itself home to 30,000, many of them poor or uneducated. Sanitation would suffer and disease would spread. The city would tear itself apart as the rich hid within their houses and the pour died in the streets.