Script preview: How do cities grow? (Patreon)

How do cities grow? On the surface, this question has a pretty simple answer. Cities grow out. They start out small, and as more people move in, they get bigger. Sure, cities grow up, too, but here in the United States cities really grow out. But there’s more to it than that. Cities grow out faster now than they did 150 years ago. And they don’t always grow evenly out from the center. Why? If you’re interested in finding out, or just want some tips on how to make a more realistic Cities: Skylines city, stay tuned.

The short answer to all of those questions is transportation. It makes sense — transportation networks form the skeleton and circulation system for the city, in the same way your bones give you your shape. But unlike your body, cities started out growing slowly and have increased their growth rate. How did transportation make this happen?

It happened because how we move around cities has changed over time, and these changes have come about rapidly in recent history. Each new transportation mode reshapes the city and opens up new opportunities for development. 

So let’s talk about the four major eras of city growth, all appropriately named after the transportation modes that were the prominent at the time. The first era was the Walking-Horsecar Era, from 1800 to 1890. And really, you could stretch this era back to the dawn of cities. Before the car, before mass transit, most everyone walked. This meant that cities couldn’t be bigger than it would be feasible for someone to walk 30 minutes from the periphery to the center. This was the size limit of cities really from the dawn of civilization until about the 1820s and 1830s. 

It was at this point that the Industrial Revolution was really starting to fundamentally change cities. They were no longer just markets for goods grown in the hinterland but industrial centers. The United States began to urbanize and draw people in from the countryside and immigrants from other countries. 

Cities began to get more and more crowded, as the walking limit for city size made it hard to accommodate newcomers. Commutes from the periphery expanded to 45 minutes, growing the city a little bit. 

Horses were pressed into use, first pulling omnibuses, which could be described as urban stagecoaches. They were slower than walking and only held about a dozen passengers, so they didn’t make a major impact on city size. Later people figured out that horses can pull more people faster if the car they’re pulling is riding on rails. New York was the first to implement the horse-drawn streetcar in 1852. These things could really fly; they could hit top speeds of 5 miles an hour, slightly faster than walking speed. 

But it did open up new land on the edge to development, allowing the city to grow a little bit more.

I should add that this era did have trains — steam locomotives. These trains would take the ultra rich from the city center to large, country estates away from the noise and disease of the city. But it wasn’t something most middle-class people could afford to use on a daily basis.

By 1890, US cities were bursting at the seams. Unable to grow out, cities packed more and more people into tenement buildings, creating dangerous and unsanitary conditions. It was just at that time that a new transportation system burst on to the scene and allowed cities to get even bigger.

That brings us to the Electric Streetcar Era, from 1890 to 1920. Electric streetcars replaced the horse-drawn streetcar as they were so much better in every respect. They could go 15 miles per hour, carry more passengers, and they didn’t rely on horses that could die of disease or poop on the streets. 

The added speed and capacity opened up a large amount of new area on the edge for residential development. The growth pattern of this era was different from the Walking-Horsecar Era. Most of the growth around the edge in the last era was relatively uniform because people would just build on the edge so long as the distance to the center was still walkable. In the Electric Streetcar Era, streetcar lines fanned out into the countryside and streetcar suburbs popped up in a few blocks in all direction from the stops. The areas between the lines never grew out; streetcar operators rarely built lateral lines. Thus the development stopped once the neighborhood got too big for someone to conveniently walk to the trolley line. 

Streetcars utterly transformed cities in a way that would only happen again a couple of eras later. Streetcar cities were true metropolises, some more than 20 miles in diameter, and the streetcars were an efficient means of moving people through them. 

The streetcar era was relatively brief, and replaced by another short era, the Recreational Automobile era of 1920 to 1945. It’s hard to underestimate how much Americans fell in love with the car in this era. Companies like Ford were putting out cheap vehicles middle class families could buy. And cars meant freedom! No waiting for a streetcar and no need to live mear streetcar line, either. 

Cars could go in any direction, whenever you wanted, and it could do so pretty fast. The Model T could top out at 45 miles per hour with the wind at its back. That’s three times faster than the streetcar. It’s no surprise that urban Americans made the switch to cars as soon as they could afford it; the streetcar never really stood a chance. And this new mobility opened up even more land for development. Even more land on the periphery could be opened for development as new roads spread into the countryside. Unlike streetcar lines, cities did build lateral roads and new development completely filled in all available space. 

This car completely changed the design of urban regions. The first two eras needed a focal point, a central business district to work. Streetcar lines started in the suburbs and brought you downtown. The car meant that people could quickly get to any point in the metropolis, and job growth began to occur outside the central business district. This was the beginning of the modern poly-centric metropolis. 

When the GIs returned from World War II in 1945, they changed the relationship between transportation and land use again, and brought us the final, modern era: the Freeway Era. While the other eras were defined by a novel mode, walking, streetcars, and cars, this era is all about the complete dominance of the car. It’s like they made the car go to 11. 

In the Recreational Automobile Era, cities built infrastructure for cars. Parkway systems, bridges, and tunnels were built to improve commutes for drivers. But after the war, states began to build proper highways in earnest. And the watershed year was 1956, when the federal government passed the Interstate Highway Act. 

With seemingly unlimited funding from the feds, states took advantage and built a massive network of freeways. Freeways connected far flung cities, they ringed urban centers, and they destroyed neighborhoods as they were jammed into central business districts. When they weren’t jammed with traffic, they allowed cars to go 60 miles per hour or more. This added speed and convenience meant that a huge swath of countryside around urban areas was now ripe for development. As the car allowed for lateral movement, development filled in between freeways except at the edge of the metropolis, where development continued out like tentacles reaching for the next metropolis. 

Freeways also matured the concept of the poly-centric metropolis. Beltways often made it easier for someone living in the suburb to go to work in a different suburb instead of driving downtown. These new job centers, sometimes called edge cities or suburban downtowns often popped up near freeway interchanges. Malls and shopping centers also gravitated to the interchanges. 

The result was a hollowing out of the city center. More people lived in the suburbs than the center city, and now they worked in the suburbs, too. The city originally built for walking and transit was ill-equipped to compete in a car-centric world, and adding freeways to the center seemed to speed up the desertion. 

So here’s our final map. Cities Skylines players take note. This is the general pattern of growth in US cities. And I want to leave you with a few thoughts about what the next era could bring. Autonomous vehicles are probably the best bet for our next era. One could imagine that they could grow city boundaries even further, as long commutes become more bearable. Perhaps people won’t even consider them commutes. Without the need to drive, people could eat dinner, get work done, or socialize during their drive and a commute of an hour or more wouldn’t be so bad.

I also made it seem like the eras were inevitable, as if the new transportation systems were almost like a force of nature. And it’s true to some extent, but we can also choose what our next era will be. Will it be the multimodal era, with transit, bikes, walking, and scooters rising as people rediscover the city center? It can be if we really want it to.