Atlanta has some of the worst traffic in the United States. Drivers there average two hours each week mired in gridlock, hung up at countless spots, from the constantly clogged Georgia 400 to a complicated cluster of overpasses at Tom Moreland Interchange, better known as “Spaghetti Junction.” The Downtown Connector — a 12-to-14-lane megahighway that in theory connects the city’s north to its south — regularly has three-mile-long traffic jams that last four hours or more. Commuters might assume they’re stuck there because some city planner made a mistake, but the heavy congestion actually stems from a great success. In Atlanta, as in dozens of cities across America, daily congestion is a direct consequence of a century-long effort to segregate the races.

For much of the nation’s history, the campaign to keep African-Americans “in their place” socially and politically manifested itself in an effort to keep them quite literally in one place or another. Before the Civil War, white masters kept enslaved African-Americans close at hand to coerce their labor and guard against revolts. But with the abolition of slavery, the spatial relationship was reversed. Once they had no need to keep constant watch over African-Americans, whites wanted them out of sight. Civic planners pushed them into ghettos, and the segregation we know today became the rule.

At first the rule was overt, as Southern cities like Baltimore and Louisville enacted laws that mandated residential racial segregation. Such laws were eventually invalidated by the Supreme Court, but later measures achieved the same effect by more subtle means. During the New Deal, federal agencies like the Home Owners’ Loan Corporation and the Federal Housing Administration encouraged redlining practices that explicitly marked minority neighborhoods as risky investments and therefore discouraged bank loans, mortgages and insurance there. Other policies simply targeted black communities for isolation and demolition. The postwar programs for urban renewal, for instance, destroyed black neighborhoods and displaced their residents with such regularity that African-Americans came to believe, in James Baldwin’s memorable phrase, that “urban renewal means Negro removal.”

This intertwined history of infrastructure and racial inequality extended into the 1950s and 1960s with the creation of the Interstate highway system. The federal government shouldered nine-tenths of the cost of the new Interstate highways, but local officials often had a say in selecting the path. As in most American cities in the decades after the Second World War, the new highways in Atlanta — local expressways at first, then Interstates — were steered along routes that bulldozed “blighted” neighborhoods that housed its poorest residents, almost always racial minorities. This was a common practice not just in Southern cities like Jacksonville, Miami, Nashville, New Orleans, Richmond and Tampa, but in countless metropolises across the country, including Chicago, Cincinnati, Denver, Detroit, Indianapolis, Los Angeles, Milwaukee, Pittsburgh, St. Louis, Syracuse and Washington.

While Interstates were regularly used to destroy black neighborhoods, they were also used to keep black and white neighborhoods apart. Today, major roads and highways serve as stark dividing lines between black and white sections in cities like Buffalo, Hartford, Kansas City, Milwaukee, Pittsburgh and St. Louis. In Atlanta, the intent to segregate was crystal clear. Interstate 20, the east-west corridor that connects with I-75 and I-85 in Atlanta’s center, was deliberately plotted along a winding route in the late 1950s to serve, in the words of Mayor Bill Hartsfield, as “the boundary between the white and Negro communities” on the west side of town. Black neighborhoods, he hoped, would be hemmed in on one side of the new expressway, while white neighborhoods on the other side of it would be protected. Racial residential patterns have long since changed, of course, but the awkward path of I-20 remains in place.

A MARTA station under construction on the edge of downtown Atlanta, 1978. Charles Pugh/Atlanta Journal Constitution, via Associated Press

By razing impoverished areas downtown and segregating the races in the western section, Atlanta’s leaders hoped to keep downtown and its surroundings a desirable locale for middle-class whites. Articulating a civic vision of racial peace and economic progress, Hartsfield bragged that Atlanta was the “City Too Busy to Hate.” But the so-called urban renewal and the new Interstates only helped speed white flight from Atlanta. Over the 1960s, roughly 60,000 whites left the city, with many of them relocating in the suburbs along the northern rim. When another 100,000 whites left the city in the 1970s, it became a local joke that Atlanta had become “The City Too Busy Moving to Hate.”

As the new suburbs ballooned in size, traffic along the poorly placed highways became worse and worse. The obvious solution was mass transit — buses, light rail and trains that would more efficiently link the suburbs and the city — but that, too, faced opposition, largely for racial reasons. The white suburbanites had purposefully left the problems of the central city behind and worried that mass transit would bring them back.

Accordingly, suburbanites waged a sustained campaign against the Metropolitan Atlanta Rapid Transit Authority (MARTA) from its inception. Residents of the nearly all-white Cobb County resoundingly rejected the system in a 1965 vote. In 1971, Gwinnett and Clayton Counties, which were then also overwhelmingly white, followed suit, voting down a proposal to join MARTA by nearly 4-1 margins, and keeping MARTA out became the default position of many local politicians. (Emmett Burton, a Cobb County commissioner, won praise for promising to “stock the Chattahoochee with piranha” if that were needed to keep MARTA away.) David Chesnut, the white chairman of MARTA, insisted in 1987 that suburban opposition to mass transit had been “90 percent a racial issue.” Because of that resistance, MARTA became a city-only service that did little to relieve commuter traffic. By the mid-1980s, white racists were joking that MARTA, with its heavily black ridership, stood for “Moving Africans Rapidly Through Atlanta.”

[To get updates on The 1619 Project, and for more on race from The New York Times, sign up for our weekly Race/Related newsletter.]

Even as the suburbs became more racially diverse, they remained opposed to MARTA. After Gwinnett voted the system down again in 1990, a former Republican legislator later marveled at the arguments given by opponents. “They will come up with 12 different ways of saying they are not racist in public,” he told a reporter. “But you get them alone, behind a closed door, and you see this old blatant racism that we have had here for quite some time.”

African-American and white passengers on an Atlanta Transit Company trolley on April 23, 1956, shortly after the outlawing of segregation on all public buses. Horace Cort, via Associated Press

Earlier this year, Gwinnett County voted MARTA down for a third time. Proponents had hoped that changes in the county’s racial composition, which was becoming less white, might make a difference. But the March initiative still failed by an eight-point margin. Officials discovered that some nonwhite suburbanites shared the isolationist instincts of earlier white suburbanites. One white property manager in her late 50s told a reporter that she voted against mass transit because it was used by poorer residents and immigrants, whom she called “illegals.” “Why should we pay for it?” she asked. “Why subsidize people who can’t manage their money and save up a dime to buy a car?”

In the end, Atlanta’s traffic is at a standstill because its attitude about transit is at a standstill, too. Fifty years after its Interstates were set down with an eye to segregation and its rapid-transit system was stunted by white flight, the city is still stalled in the past.