When Nelson Mandela died, it reignited ideas that had been floating around in my brain for awhile: comparative segregation studies, if you will, between South Africa and the United States, in particular Chicago.

It started in the wake of the Oscar Pistorius case, when the Olympic runner's self-defense highlighted South Africa's deep urban problems, which are more severe but not unlike Chicago's. Johannesburg has a murder rate of 30.5 per 100k and Cape Town has one of 46 per 100k, comparable to Chicago's 1992 rate of 34 per 100k.

As in Chicago, its homicides are geographically concentrated. As in Chicago, South Africa's cities are immersed in a country with a prevalent gun culture. And both places share a long history of segregation. (Eerily, apartheid became law after the victory of South Africa's National Party in 1948, the same year the segregationist Dixiecrat party took three states for Strom Thurmond.)

In America, there was no national system of apartheid reaching well into the late 20th century, and no Mandela, no single person, to focus and fight an explicit policy of state-imposed segregation. Yet both places, at the end of the century, ended up in similar places, with similar lines drawn and similar problems. How did it happen?

I'd read a fair amount about the history of segregation in Chicago, from Thomas Sugrue to Steve Bogira to Beryl Satter to Ta-Nehisi Coates. But South Africa was still a blank; Nelson Mandela was released from prison when I was 10; the word "apartheid" was chilling but distant, like something from a ghost story.

Fortunately, someone wrote the book on this topic: Segregation: A Global History of Divided Cities, by SUNY-Buffalo professor Carl Nightingale. (He began work on the book while a visiting faculty member at the University of Wisconsin-Milwaukee, which as of 2010 was located in the most segregated metro area—between black and white, at least—in America.) The book covers a number of places throught the world and world history, but almost half the book is devoted to Johannesburg and Chicago, which he describes as "national clearinghouses for techniques that reengineered these imported devices [of segregation] in ways that sparked movements for racially exclusive neighborhoods that were unparalled anywhere else in the colonial world."

Recently Nightingale talked with me about how the two nation's paths over the past couple centuries. They differ in critical ways, but their parallels are not coincidental.

In the beginning of their modern societies, both the U.S. and South Africa begin with a frontier culture matched by policies of native resettlement, Nightingale says:

"Their differences really go back, I argue, to the 19th century. There's two very different dynamics in black-white politics in both societies. In South Africa, the main matrix of black-white politics is a story of conquest and land dispossession. It's the British, and the Boers, the Afrikaaners, who are taking over the land that belonged to, collectively, the various different black peoples of South Africa, more or less the way that, in the United States whites took over Native American land. In a sense, a kind of law of conquest followed."

This is critical for understanding how South Africa ended up with an explicit national policy of enforced segregation, while the United States evolved a patchwork of subtle laws—"camouflaged segregation," to use Nightingale's term—that resulted in similar patterns. As he describes, black-white segregation in South Africa has as much in common with white-Native American segregation in the United States; politically, legally, and logistically, South Africa's "Group Areas" are more like urban versions of reservations than the segregated urban areas of America.

A second historical precedent determines this distinction. Black-white political relations in 19th-century South Africa were defined by acts of control; in America, they were determined by acts of liberation: "the regional civil war left one part defeated, the South, and a victorious North eager to get black votes to vote on its side," says Nightingale. "And what they did during Reconstruction is they enfranchised black men. That, and the 14th Amendment made it very clear that blacks had civil rights; and the15th, voting rights."

The history of Reconstruction demonstrates how vulnerable these protections were, but as they did establish legal and political barriers that were non-existent in South Africa. "What that did was create a legal framework, a constitutional framework," Nightingale says, "where blacks had very limited rights to the land, very limited rights of property, very little voting capacity—only a very small number of blacks could vote, in some parts of the country and not in big parts of the country—and very, very limited civil rights. That's a big difference."

Undermined as those barriers were by Jim Crow laws, they provided a foundation for activists and politicians to build on, such as the tremendous legal battles fought against entrenched legal segregation in the 20th century.

In this sense, South Africa is a cautionary alternate history of the United States: what would have happened if the Dixiecrats had won. Yet the result, at the end of the 20th century, was more like a doppelganger than an evil twin, a quiet apartheid.

Nightengale, as mentioned, describes what happened in America as camouflaged. Another way to think of it is "submerged," borrowing the useful term from Suzanne Mettler's The Submerged State. The submerged state refers to government functions that citizens only know are government functions if they're paying various degrees of attention: Medicare should be an obvious one, but things like subsidized student loans, mortgage deductions, and the earned income tax credit are the opaque hand of the controlled market shaping America.

During the first half of the 20th century, the tools of the submerged state were used to shape the country along racial lines. "You can't have racial laws," Nightingale says. "But you can have racial non-laws, namely the restrictive covenants. They're non-laws, but they are racist, they're racially clear. And the Supreme Court says that's okay in 1926—sort of ambiguously. Then you can have non-racial laws, so you can have zoning, you can have mortgage supports, you can have public housing, you can have urban renewal, all these different kinds of laws that are technically non-racial in the books, but can be implemented in racial ways on the local level to various different means. That's where this submerged or camouflaged segregation comes about."

In 1910, the Supreme Court invalidated explicitly racial segregation in Buchanan v. Warley. As George Mason law professor David E. Bernstein writes (emphasis mine), "the decision inhibited state and local governments from passing more pervasive and brutal segregation laws, akin to those enacted in South Africa." This essentially made top-down, state-enforced residential segregation illegal.

But in 1926, it essentially permitted private residential segregation in Corrigan v. Buckley. In 1921, a group of white homeowners agreed not to sell their houses to blacks. The next year, one of the homeowners tried to sell to a black couple. The Supreme Court refused to hear the case, "stating that constitutional amendments were applicable only to state action rather than individual action, that there was no substantial constitutional or statutory question giving the Court jurisdiction of the appeal, and that it thus could not determine that the covenant was void and discriminatory."

Corrigan v. Buckley reveals where legal segregation in the former British colonies of South Africa and America, otherwise so different, converge through an inherited legal framework. "Developers in London—actually very, very early on, as early as the late 17th century—were putting in restrictive covenants on deeds," says Nightingale. "And this was an effort to keep poor people off of the new squares that were developing west of London after the Fire. And those, later on, became part of a huge body of jurisprudence, and they became essential to the whole process of suburban development in Britain, and developers in the United States and South Africa took those techniques with them when they built housing in the areas around South African and U.S. cities."

It would take years to overturn the non-precedent set by Corrigan, years that encompassed most of the Great Migration.

The restrictive covenant, during a period of intense immigration and in-migration, permitted a private detour around the prohibition of segregation. That principle was absorbed by the real-estate industry, and written into their professional guidelines. In 1924, Nathan William MacChesney, chief council of the Chicago-based National Association of Real Estate Boards, enforced residential segregation in the NAREB's professional code of ethics, which prevented agents from "introducing into a neighborhood… members of any race or nationality… whose presence will be clearly detrimental to property values in that neighborhood."

MacChesney had "the halo of scientific endorsement," as Nightingale writes, from Richard T. Ely, the prominent University of Wisconsin (and later Northwestern) economist, founder of the American Economic Association and director of the Institute for Research on Land Economics and Public Utilities. Both men "flirted openly with Social Darwinism and eugenics." And both turned Chicago into a hub of legal and economic theories bolstering segregation.

MacChesney wrote the infamous "Standard Form, Restrictive Covenant,"  which immediately spread throughout the city. One of Ely's proteges, Frederick Babcock, a property appraiser in his father's Chicago firm, wrote The Appraisal of Real Estate for Ely's institute, blending racial theory into the science of home values. A decade later, in 1934, Babcock became the chief appraiser for the new Federal Housing Administration, introducing the ideas in the NAREB circle to federal lending: "The FHA’s underwriting standards, from their earliest incarnations, were premised on the unshakable belief handed down from the work of Fredrick Babcock and Homer Hoyt [a University of Chicago real-estate economist] that racial integration structurally leads to the decline in housing values."

It's one of most difficult questions in the study of Chicago history and sociology: how did a northern city, a beacon for blacks migrating north to seek opportunity become so infamous for its segregation? Perhaps it was the chance of historical timing. The city's population exploded in a still-developing city as the flourishing of racial and eugenic "science" overlapped into the nascent fields of sociology and real-estate economics.

"There is a regional Midwestern thing where all the cities with the highest segregation indexes until this day are all in the Midwest," says Nightingale. "I'm not sure exactly why that is true. But it is true that Chicago had this enormous and booming land industry that the Chicago real estate board—which is founded in the 1890s—could claim, plausibly, that it was the most powerful real estate organization in any city, and in the world, and was then strong enough to then create a national organization located on Michigan Avenue. And in so doing really fell into the position, after the demise of Buchanan vs. Worley, as the center of power that people who wanted to divide cities had to rely upon."

The story of segregation in South Africa is, metaphorically, a black-and-white one, with world-historical heroes and villains. In Chicago, it's hidden in the gray prose of bureaucracy. Which goes some way towards explaining something that Steve Bogira wrote after the death of Nelson Mandela:

Americans were eager to condemn South Africa's apartheid system, Massey and Denton observed, but less willing "to acknowledge the consequences of their own institutionalized system of racial separation." And unwilling to even talk about it, the authors noted: "The topic of segregation has virtually disappeared from public policy debates. . . . Residential segregation has become the forgotten factor of American race relations."

Twenty years later, is that any different? When was the last time you heard Mayor Emanuel or President Obama talk about racial segregation?

American segregation arose from the submerged state—a thicket of covenants, deeds, underwriting manuals, and obscure professional publications, disguising a subtly shaped process as a natural order. Unwinding its history, document by document, has taken years; addressing it will take many more.