Concentrated poverty and racial segregation in American cities are tremendously knotty problems, problems inherited across generations that are hard to solve for unspoken reasons of politics and history and race.

But here is one fairly simple truth that we need to acknowledge -- but seldom do -- to create any kind of sustainable policy solutions, whether they take the form of housing vouchers or pre-K education or "promise neighborhoods": "When it comes to housing and race," says Sherrilyn Ifill, the president and director-counsel of the NAACP Legal Defense and Educational Fund, "there really is no such thing as chance or accident."

She was speaking this week at a discussion on concentrated neighborhood poverty hosted by the Economic Policy Institute. And what she means by this is that suburbs didn't become predominantly white and upper income thanks solely to market forces and consumer preferences. Inner city neighborhoods didn't become home to poor minority communities purely through the random choices of minorities to live there. Economic and racial segregation didn't just arise out of the decisions of millions of families to settle, by chance, here instead of there.

The geography that we have today -- where poverty clusters alongside poverty, while the better-off live in entirely different school districts -- is in large part a product of deliberate policies and government investments. The creation of the Interstate highway system enabled white flight. The federal mortgage interest deduction subsidized middle-income families buying homes there. For three decades, the Federal Housing Administration had separate underwriting standards for mortgages in all-white neighborhoods and all-black ones, institutionalizing the practice of "redlining." That policy ended in the 1960s, but the patterns it reinforced didn't end with it.

"Exclusionary zoning" to this day prevents the construction of modest or more affordable housing in many communities. Decisions about where to create and whether to fund transit perpetuate these divides. Government ideas about how to house the poor lead to Pruitt-Igoe and Cabrini-Green, and then government's fleeting commitment to those projects led to their disintegration.

Policies today that don't meet (and recognize) these long-running forces with a comparable commitment are likely to be overcome by them.

"For me," Ifill says, "it’s very important to remember that if you pull the thread long enough -- when we’re talking about housing and race in particular -- you get to a point where actions were compelled or imposed in ways that have generational consequences that we continue to live with today."

She gave a good illustration of this from the life of Robert Carter, the black civil rights lawyer who helped argue Brown v. Board of Education before the Supreme Court before becoming a federal judge himself. Carter's own family was part of the Great Migration of southern black families to the North, where so many -- his family included -- ended up in Newark, N.J. Here is Ifill recounting the story Carter used to tell about this:

"Many black families were on the train, and when the train conductor announced the station 'Newark,' many of them thought that the conductor said 'New York.' And so they got off the train. And then they didn’t have the money to get to New York, and so they stayed there. And that was the story of how his family ended up in Newark.

"So that sounds like chance. That sounds serendipitous," Ifill says. "But why were they on the train? Why were they leaving the community that they came from in the South?"