Chicago perceives itself, accurately, as a hypersegregated city—and a still-segregated, if less so, metropolitan area. Notoriously so; as the city's crime problems continually make national news, its intense segregation is infamous, cropping up even in seemingly unrelated stories.

So it tends to surprise people, I think, when they learn that, if anything, segregation is even more stark in its smaller, quieter neighbor to the north: Milwaukee, where Chicago's metropolitan borders, as sometimes defined, end. The Milwaukee area (including Waukesha generally ranks number one in indices of racial segregation, and number one or very high in indices of concentrated poverty.

This week the Journal-Sentinel kicked off another exploration of the city's segregation—in this case, political segregation, and the contrast to Chicago is even more extreme. In Chicago, the city is obviously heavily Democratic, but the suburbs are a battleground, and actually less ideologically polarized than they used to be. But as the Journal-Sentinel's Craig Gilbert demonstrates, the Milwaukee metro is starkly divided, more so than almost any other metro in America, and growing more polarized.

It's presented as a "modern-day clash between red and blue," a "partisan microcosm of the nation." But it's worth considering the possibility that these fault lines go much farther back, and that everything else—politics, infrastructure, housing—rearranged themselves along those lines.

Go all the way back to 1964. George Wallace, the segregationist Dixiecrat from Alabama, believes he has a shot at the presidency, but has neither money, nor an organization, nor the establishment political support to obtain either. (When he begins his campaign, he has a mere $800 in the bank.) Like any underfunded, unorganized candidate, Wallace has to build momentum before he gets money to build an organization. And to prove his bona fides in the North, he chooses primaries borderland states of Indiana and Maryland, and… Wisconsin.

And of those three states, Wallace's true breakthrough was in Wisconsin. And out of all of Wisconsin, Wallace got his strongest boost—with no money, with a suburban housewife as his primary organizer—in Milwaukee. 50 years ago last month, Wallace packed Serb Memorial Hall and got "the best reception I've ever gotten." Wallace later said that "if I ever had to leave Alabama, I'd want to live on the south side of Milwaukee."

Wallace took home a quarter of the vote in the Wisconsin primary, one-third of the Democratic vote, which may not sound like a lot, but it was twice the seemingly optimistic total his main organizer, aforementioned Oshkosh housewife Delores Herbstreith, predicted—a prediction much higher than establishment operatives expected. "It felt like an earthquake," Rick Perlstein writes. "But media outlets did their best to argue it meant nothing at all."

While he made a stir at Serb Hall—and its the city's near-south suburbs that have trended the most Republican—Wallace's support was geographically and economically more diverse than that appearance suggests:

The press linked Wallace most closely with blue-collar ethnic whites, especially on the South Side of Milwaukee. But the actual results were complicated. Wallace did run strongly on the South Side—and might have polled even better except that organized labor campaigned against Wallace based on his labor record as governor. Post-voting analysis showed that eight Milwaukee neighborhoods that were more than three-quarters blue collar had a lower percentage of votes for Wallace (33 percent) than eight neighborhoods that were almost half white collar (42 percent). Throughout the metropolitan area, Wallace's appeal crossed ethnic, class, and party lines as voters in Republican neighborhoods in Milwaukee, Waukesha, and Ozaukee counties more consistently voted for Wallace than voters in Democratic neighborhoods. Due to significant crossover voting, the affluent and Republican county of Waukesha led the state in the proportion of voters (33 percent) for Wallace. Within Milwaukee County, three white, affluent suburbs to the north and west of the city (Wauwatosa, Brown Deer, and Glendale) gave a plurality of their votes to Wallace.

Race undoubtedly played a role, and it's usually the reason given for Wallace's rise. But it was not the only reason for his relative victory:

In the staunchly Republican Ninth Congressional District, embracing affluent, white-collar suburban Milwaukee, Wallace voters were motivated both by their opposition to open housing and their desire to embarass their Democratic governor…. Suburban Republicans, who opposed the civil rights bill and Reynolds' open housing proposal, were also hostile to Governor Reynolds because of his stands on controversial issues. Reynolds' reapprortionment bill had reduced suburban representation in the legislature. His proposals for accelerated highway construction and increased state aid to local school districts in rural Wisconsin had threatened to increase suburban taxes.

Delores Herbstreith and her husband, prior to their work with Wallace, had worked both with Joseph McCarthy and on an earlier grassroots movement for the Liberty Amendment, which would have abolished the federal income tax. The Herbstreiths built a network of conservative activists and voters, well before the apex of the Civil Rights Movement, based on anticommunism and low taxes. The Milwaukee area, of course, had an immense number of Eastern European immigrants, a natural audience for anticommunism that Wallace played to.

Wallace's rhetoric, Joseph Lowndes writes, "linked economic libertarians, poor and middle-class white southerners, McCarthyite anticommunists, and white ethnics threatened by neighborhood and job integration." The governor's Southern labor policies were a barrier, but unions were on the precipice of an intense decline, and the decline of that form of upward mobility would make others—housing values, schools, taxes—even more important to his constituency.

Meanwhile, the structure of Milwaukee was changing, due to—with some irony, given opposition to Governor Reynolds's highway-building—the rise of the interstate system. Clayton Nall, an associate professor in Stanford's history department, has done some fascinating research on the rise of Republican voting in Milwaukee's suburbs as it relates to the growth of interstates in the region. As they spread, Republican voters followed the asphalt.

Those are the voting patterns in the 1952, 1980, and 2008 presidential elections; the dotted lines are interstates. The pattern of the Republican periphery is already there, but the areas where it grows in intensity line up with interstate construction. Meanwhile, the Republicans in the city center virtually disappear. Waukesha County—the one that went heaviest for George Wallace in 1964—grew, according to Nall, by 386 percent from 1940-2000. Milwaukee's population grew by about 9,000 over that period.

Nall focuses in on Brookfield, in Waukesha County, and the vote pattern is remarkable.

The dotted line coincides with Wallace's successful primary, but represents the completion of I-94. I had to check Nall's prose to make sure I wasn't misreading the chart: "the largest boom in the city’s voting-age population occurred only after the completion of Interstate-94 on the city’s southern boundary in 1964. Between 1964 and 1968, the number of Republican votes cast in Brookfield nearly doubled, while the Democratic vote total held roughly constant."

In that sense, the Journal-Sentinel's Gilbert is very smart to look not just at race, but density:

In the Milwaukee metro area, density and distance from downtown Milwaukee are actually much better barometers of a community's politics than income or education. Well-to-do inner suburbs are trending blue (Fox Point, Whitefish Bay, Bayside), while well-to-do outer suburbs remain very red (Mequon, Delafield, Cedarburg). The GOP suburban belt includes not just affluent communities full of white-collar professionals but lots of blue-collar towns with median incomes under $70,000.

Milwaukee isn't alone in this pattern. The Wall Street Journal recently took a look at "citifying suburbs," or "mature," inner-ring suburbs building up around the nation's major cities. Residents are looking for a greater combination of urban and suburban qualities, which include greater density and the infrastructure to support it. When Ian Spula gathered the city's best neighborhoods and the metro's best suburbs for Chicago, he looked at "ease of transportation downtown, giving extra points for those that have several el stops and at least one Metra stop." A study last year co-sponsored by the National Association of Realtors found that real estate values did best in walkable areas near public transportation. Recently Chicago suburbanites flipped years-long trends, declaring their support for investing in public transit, with the percentage in favor rising from 34 percent to 52 percent in a decade. Meanwhile, the current-issue GOP's opposition to public-transit funding is dividing regional Republican leaders along suburban and exurban lines.

There are a lot of theories as to why dense areas trend Democratic, but a likely cause is that density requires more intensive government services. (Not just public transportation but sanitation as well: one of Gilbert's subjects calls the Republican exurbs the "septic tank belt.") More government services require more rules, more regulation, more taxation—the kind of taxation that drove the backlash against Wisconsin's governor in 1964 into the hands of George Wallace.

The "big sort" that Gilbert identifies was growing for decades, but in order to sort, people have to be able to move. As Nall contends, sorting was simply more difficult prior to the second half of the 20th century, before the advent of "government policies that reduce the cost of living in a homogeneous community by increasing mobility, shrinking space in metropolitan areas, and acting as a catalyst for the self-selection process."

In other words, people follow polarization, then polarization follows along behind: "sorting can generate additional political conflict by increasing the alignment between place and political ideology, and it can make citizens who live in a homogeneous environment more politically extreme than they would have been in the absence of sorting (i.e., through contextual effects)."

That divide fanned out along the interstate system, which arguably intensified the polarization seen in Milwaukee and its suburbs. But the political fault lines were there, waiting for physical lines to follow.