This is exactly what happened in Syracuse, New York. The city had big dreams of becoming an East Coast hub, since it was close to New York City, Pittsburgh, Cleveland, and Boston. (In the early days of the car, close was relative.) Use federal funds to build a series of highways, planners thought, and residents could easily get to the suburbs and to other cities in the region. After all, who wouldn’t want to live in a Syracuse that you could easily leave by car? And, if they put the highway in just the right place, it would allow the city to use federal funds to eradicate what they called a slum area in the center city.

That neighborhood, called the 15th Ward, was located between Syracuse University and the city’s downtown. It was predominantly African American. One man who lived there at the time, Junie Dunham, told me that although the 15th Ward was poor, it was the type of community that you often picture in 1950s America: fathers going off to jobs in the morning; kids playing in the streets; families gathering in the park on the weekends or going on Sunday strolls. He remembers collecting scraps from the streets and bringing them to the junkyard for pennies, which he would use to buy comics.

To outsiders, though, the 15th Ward was the scene of abject poverty close to two of Syracuse’s biggest draws—the university and downtown. They worried about race riots because so many people were crowded into the neighborhood and prevented from going anywhere else. They decided that the best plan would be to tear down the 15th Ward and replace it with an elevated freeway.

The completion of the highway, I-81, which ran through the urban center, had the same effect it has had in almost all cities that put interstates through their hearts. It decimated a close-knit African American community. And when the displaced residents from the 15th Ward moved to other city neighborhoods, the white residents fled. It was easy to move. There was a beautiful new highway that helped their escape.

But this dynamic hurt the city’s finances, too. As suburbs grew, they broke off from cities, taking with them tax revenues, even though their residents still used city services. Although the Syracuse region was relatively healthy, the city started to get very sick.

Between 1940 and 2000, the population of the city of Syracuse shrank 30 percent, from about 205,000 to 147,000. The population of Onondaga County, where Syracuse is located, grew 55 percent, from 295,000 to 458,000.

Even today, the region is continuing to sprawl. The population of Onondaga County peaked in 1970 and has stayed even since then. But residents are moving farther and farther out. The county has added 7,000 housing units, 147 subdivisions, and 61 miles of new roads since 2000. Developers build 160 units a year in areas that were once rural. That’s costing the county money and resources as it adds sewer systems, water pipes, and stormwater drainage to far-flung subdivisions. As the county spends money, the city is struggling to come up with enough revenue for essential things like mass transit and schools.