Fifty years ago on April 11, Congress enacted the Fair Housing Act, the last of the three great civil rights laws of the 1960s. Along with the Civil Rights Act of 1964 and the Voting Rights Act, it was an attempt by Congress to translate the movement led by the Rev. Dr. Martin Luther King Jr. and others into enduring statute. But it also has the more dubious distinction of being the most contested, most ignored and, at times, most misunderstood of those laws.

For most of the 20th century, an array of forces worked to divide American communities into black and white quarters. Some involved explicit discrimination, including racial redlining in federal mortgage insurance, and real estate covenants that restricted home buyers by race. But some were more subtle, like the steering by real estate agents of racial minorities into certain neighborhoods, biased lending and underwriting, and the concentration of low-income housing in low-income neighborhoods.

By the late 1960s, racial tensions came to a head, marked by civil disturbances that the bipartisan Kerner Commission attributed to the growth of “two societies, one black, one white — separate and unequal.” The fair housing bill, which had been filibustered for many years by segregationist senators, received a critical push from this report. Provisions that would have exempted single-family homes were defeated, and the law passed the Senate.

Then, on April 4, 1968, Dr. King was assassinated. His death shook the nation, setting off another round of disturbances. Something had to be done — not just about America’s ugly history of housing discrimination but also about the divided system that had led the nation to this awful moment. The assassination dislodged the stalled housing bill from the House Rules Committee, and one week later the Fair Housing Act was signed into law.