As affordable housing becomes an ever more prominent progressive cause — thanks to economic segregation, a broad swell in housing prices and rising rents in the neighborhoods where progressive media people hang out — some rather odd fault lines are forming.

Some writers and activists have decided that a policy agenda associated with race equality activists since the 1960s is, in fact, the province of — to quote a Gawker piece from July — “tech bloggers, Redditors, Hacker News trolls, and politically-connected venture capitalists.”

The policy in question is easing the laws that make it illegal to build more housing, otherwise known as zoning. Opponents see this as an easy way for developers to build yuppie condos and cafes with $4 toast.

That’s understandable. Most new development in places like San Francisco and New York is, in fact, built and priced for the wealthy.

But to stop there also demonstrates a striking ignorance of decades of housing battles on the front lines of civil rights work. For years, activists and researchers have known that restrictive zoning is among the most powerful forces behind racial and economic segregation in the country.

This is for two reasons. First, in many neighborhoods, zoning laws prevent the construction of low-cost housing by, for example, allowing only single-family homes instead of apartments. Second, zoning laws restrict the total amount of housing that can exist in any given area, which means that wherever well-to-do people decide to move, they will bid up the price of housing until it’s out of range of everyone else. Imagine, for example, if there were a law that only 1,000 cars could be sold per year in all of New York. Those 1,000 cars would go to whoever could pay the most money for them, and chances are you and everyone you know would be out of luck.

Researchers have found overwhelming evidence that restrictive zoning raises housing prices, not just in San Francisco and other coastal metropolises, but in suburbs and city neighborhoods across the country. The stricter a region’s zoning laws, the more segregated it is likely to be.

That result was anticipated from the very beginning. Back in the 1920s, developers sued Euclid, Ohio, arguing that zoning was unconstitutional. At first, a federal judge agreed with them, and struck down Euclid’s law. The judge pointed out that the Supreme Court had struck down racial zoning, which explicitly segregated cities based on race, only a few years before; this new form of zoning, which set aside different parts of the city for different kinds of housing, was also clearly meant to “classify the population and segregate them according to their income or situation in life.”

The U.S. Supreme Court reversed that decision, upholding zoning’s constitutionality, but not because it disagreed that the outcome would be segregation. Instead, the high court essentially argued that zoning was fine because segregation was a good thing: that people who lived in apartments were “parasites” who were trying to “take advantage of the … attractive surroundings” wealthier people could afford.

That legacy took on new importance in the aftermath of Brown v. Board of Education, when civil rights advocates noticed something interesting: White families were leaving school districts where integration might force them to share schools with black families. They weren’t moving across the country, though; they were just moving to the suburbs — and their suburban school districts.

Black people, however, were not following them, because these suburbs were generally not open to black people. This was true for a lot of reasons, but a big one was that they were simply unaffordable: The kinds of housing that people who had just been fleeced for the last three centuries could buy or rent were almost always illegal there, thanks to zoning.

So civil rights activists took up the cause of what became known as “exclusionary zoning.” (The term was applied in many places, but most often to laws that allowed only more expensive, low-density housing, and kept out smaller homes or apartment buildings.) For a very brief while, it looked like they might win some quick, major victories. After the passage of the 1968 Fair Housing Act, President Richard Nixon’s first HUD secretary, George Romney (father of Mitt), actually devised a plan to deny federal money to cities and suburbs that engaged in exclusionary zoning.

Unfortunately, as Nicole Hannah-Jones describes at the beginning of her excellent ProPublica piece on the failures of desegregation, Nixon was not exactly a racial progressive, and he quashed Romney’s plan before it could begin.

But the fight didn’t end there; it just moved to the courts and the states. The 1970s saw a tidal wave of high-profile civil rights lawsuits taking aim at restrictive zoning laws, virtually all of which were lost. Most crucially, in 1977 the Supreme Court upheld a law that banned apartment buildings in the Chicago suburb of Arlington Heights, denying an affordable housing developer’s claim that the law made integration almost impossible. (At the time, Arlington Heights had about 27 black residents out of a population of 64,000. In the nearly four decades since, its zoning has largely remained intact, and its black population is still under 1,000.)

Another case, known as Mount Laurel, resulted in a decades-long struggle between the NAACP and the state of New Jersey to strike down exclusionary zoning in the Garden State once and for all. That saga is far too complex to summarize here (“Our Town” is a good book, if you’re interested), but suffice it to say that the end result fell far, far short of what integrationists had hoped for.

The slow death of Mount Laurel’s fair housing plan marked the end of the radically ambitious efforts to overturn segregation-by-zoning. But, in places, the fight has continued. Researcher-activists such as Douglas Massey and Myron Orfield have bolstered the academic evidence that restrictive zoning laws promote segregation, and reporters such as Hannah-Jones are keeping those stories alive.

Most exciting, however, is that the Obama Administration has recently begun acting — albeit on a small scale — on Romney’s decades-old plan to use the power of the federal government to change discriminatory zoning laws. HUD has an ongoing lawsuit against Westchester County in New York, demanding, among other things, that more land be zoned for apartment buildings instead of single-family homes. And recently HUD declared that Dallas’s zoning laws are in violation of civil rights laws as well.

To be clear, even zoning reform’s most high-profile advocates don’t limit themselves to calling for fewer restrictions on private development. Even the Harvard economist Ed Glaeser, who could fairly be called a free-market sympathizer, has written that the market will never provide enough affordable housing on its own, and suggested massively expanding housing subsidies for low-income residents. Contrary to Gawker’s claims, opponents of restrictive zoning aren’t “cheerleaders for laissez-faire development” — they’re advocates for the basic civil right that people ought to be able to live where they want.

In one way, of course, it’s not surprising that this side of the story has been so thoroughly forgotten. After all, history is written by the victors, and on the whole, the mostly white, well-to-do defenders of the status quo have so far won handily.

But those who believe that housing and segregation continue to be at the heart of the American struggle for equality, it’s time to bring back this history — and in doing so, refuse to say that the fight is over.