Courtesy NASA Visible Earth catalog

Eight different ways to measure and think about what makes a city

Most often when you cross the borders of a city or town, nothing much happens. Those edges, invisible lines of jurisdictional separation, are easily ignored or forgotten as we walk, bike, and drive through a metro area. Cities can blend into one another almost imperceptibly. Development just keeps going and going in many parts of the U.S., creating urbanized entities much grander than a single city. When we think about cities, it’s increasingly inaccurate to think about them in isolation.

Our ever more interconnected, urbanized world therefore presents a challenge to academics and researchers who aim to quantify and better understand cities. Where does a city really begin and end? These days there are as many ways to measure a metro area as there are arguments for and against each one. To help visualize, let’s use Los Angeles as an example.

City Borders

Map of the boundaries of Los Angeles, courtesy City of Los Angeles Bureau of Engineering

All cities have their technical ends, and for good reason. Municipalities need to know just how far their rules can reach and where their services should go. This map shows the extent of the City of Los Angeles’s awkwardly shaped jurisdiction — where its police patrol, where its schools are located and, not insignificantly, where it gets its tax revenue. The boundaries of the city jut in an out, sometimes skipping over entire neighborhoods. Its shape is a result of politics and history, and also logistics, as can be seen in that skinny little band of city to the south that connects it to the Port of Los Angeles.


Metropolitan Areas

The Los Angeles-Long Beach-Santa Ana Metropolitan Statistical Area, composed of Los Angeles and Orange counties, courtesy U.S. Census Bureau

Being the poster child of sprawl, Los Angeles is well known for spreading itself beyond its borders. Of course, that’s not the City of Los Angeles, but the Greater Los Angeles Area—a large collection of cities big and small that center around L.A. and radiate throughout the Southern California basin. Greater Los Angeles as a concept is generally understandable, but not within the precision of the city’s hard borders. One way to put that “greater” into context is through the concept of the Metropolitan Area. These are places often centered around one big city that are made up of a number of smaller but integrated and interconnected cities. The U.S. Office of Management and Budget has created a definition of these places – Metropolitan Statistical Areas – to aid in the digestion of information like that collected in the decennial Census. 

Metropolitan Statistical Areas are defined as places that have at a high degree of economic and social integration and are centered around one or a few principal cities. These are areas with shared housing and labor markets, which the OMB defines by looking at commuting data collected by the Census.

“It’s basically a commuting region,” says William Frey, a demographer at the Brookings Institute. “They typically use counties, which is not a great unit of analysis, especially in the west because the counties are so big. But it’s the only way the data are collected in a consistent way.”

That statistical convenience creates large, blocky areas that often don’t really align with what we think of as the “greater” area around a city. The Los Angeles-Long Beach-Santa Ana Metropolitan Statistical Area, for example, is made up of Los Angeles County and Orange County, but officially does not include places like Riverside, just over the border to the east in Riverside County but hardly disconnected. For statistical purposes, including Riverside (and San Bernardino, and Fontana, and Redlands) is just too inconvenient. But in economic, commuting, and plainly physical terms, these places are just as connected to Greater Los Angeles as cities in Orange and L.A. counties.


America 2050
Map of the 11 “megaregions” of the U.S., as defined by the infrastructure-focused coalition America 2050.

One way to think about this vast urban interconnectedness is the concept of the megaregion. Developed by the Regional Plan Association’s America 2050 initiative, megaregions are large networks of metropolitan areas that are connected through their economies as well as their infrastructure and transportation flows. These are broad reaches of urban areas like the Northeast Corridor connecting from Boston to Washington D.C., and the Texas Triangle of Dallas, San Antonio and Houston.

Los Angeles is part of the Southern California megaregion, which includes Anaheim, Long Beach and San Diego, and even stretches to Santa Barbara in the north, Tijuana to the south and Las Vegas to the east. America 2050, an initiative focused on addressing infrastructural, economic, and environmental challenges in the U.S., estimates that this megaregion will have a combined population of more than 28 million people by 2025, and it’s likely that this growth will further connect the urbanized areas within. As these areas merge and their populations intermingle, America 2050 foresees growing strains on the urban system.

“From infrastructural challenges to the loss of habitat to threats to drinking water, there are potential threats from these regions growing together that can’t be tackled by our existing governance structures,” says program director Petra Todorovich.

There’s no clear way to govern a region that spans 37,000 square miles, two countries, three states and dozens of cities, but Todorovich is hoping that the increasingly shared problems of interconnected regions will encourage coalitions to form among governmental and non-governmental groups to try to find solutions.

Satellite Imagery

America 2050
Astronaut photograph of Los Angeles courtesy NASA Visible Earth catalog

As critical as shared infrastructure problems can be, what’s maybe more interesting about large groups of cities is just how far they spread. An increasingly accessible way to visualize the extent of cities is through satellite imagery. Google Earth is probably the easiest place to see cities from a satellite’s-eye view.

Earthshots is an online repository of satellite imagery that documents change over time. This is a really useful way to look at cities, especially as their populations grow and their land use spreads. This set of images shows the spread of Las Vegas over time, with imagery from 1964, 1972, 1986, 1992 and 2000. Google Earth’s Historical Imagery tool also allows this comparison over time, though it typically covers a much shorter span.

But in terms of seeing a city and its spread, probably the best use of satellite imagery is shots taken at night. The light emitted by urban centers offers a much clearer way of seeing how big a metropolitan area really is, and just how far its connections go.

In 1890, John Wesley Powell, director of the U.S. Geological Survey, created a map of the western U.S. based on its drainage areas, or watersheds. He had mapped where water was sourced and spread in the then-new western part of the country, and proposed using those natural water-based boundaries as the borders for new states. That clearly didn’t happen. But maybe it should have.

“As the political boundaries and really the rules of settlement of the west were being set, I think there was a lot of merit to those ideas,” says Dr. Robert Hirsch, a research hydrologist at the USGS.

In those days, water was the limiting factor of urbanization, but as water engineering expanded, so too did cities. See: Los Angeles. Hirsch says that the watershed as a boundary did make sense at a time, but isn’t really relevant today. Today’s low costs for transporting water means cities are no longer bounded by their watersheds.

“In many cases we’ve got cities that span multiple watersheds and in fact control water from watersheds that they’re not even located in,” Hirsch says.

Cell Phone Service Maps

Communication is another way to think about cities and how they connect. These cell phone signal heat maps offer a sort of real-time look at the shape of our urbanized and populated areas. Where there’s cell service, there are people. That’s not to say places without cell service don’t matter, but they’re probably not what we should consider a city—and that’s likely to become even more the case over time. To see a cell phone signal map like the one above of your city, check out

New Maps

Paste in Place, the maps diverge from formal city borders in favor of new ways of thinking about political, social, and natural aspects.

“I do think there’s value in the cultural history of those original boundaries,” says Sullivan. “But at the same time, thinking forward, thinking about the problems our cities face today, we should really think about those boundaries and their impact on our cities and services.”

One of his maps is based on cities sized to house 6,000 people, an ideal population for traditional town hall meeting governance. Another is organized by areas with similar geology, wildlife, hydrology, land use and vegetation. A map called “Donutowns” reorganized the municipalities based on their nearest Dunkin’ Donuts store.

“There’s a lot of value in thinking more conceptually, more artistically, more broadly about those boundaries,” says Sullivan. “Maybe they shouldn’t just be tied to municipal services.”

Or to natural systems. Or to doughnut shops. Sullivan argues that the best way to think about these places might actually be a combination of many of these methods, pulling in jurisdictional, infrastructural, political, and social concerns.

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