ARCHIVAL (WHITE HOUSE, 3-2-17):VICE PRESIDENT MIKE PENCE: The 17th Secretary of Housing and Urban Development, Dr. Ben Carson.

NARRATION: President Trumps Secretary of Housing, Ben Carson, is being sued by civil rights advocates for what they see as his failure to enforce the Fair Housing Act, a landmark law that turned 50 years old this year.

Ending housing discrimination was a key demand of activists like Martin Luther King, Jr. who in 1966 brought his protest movement north to Chicago, one of the most segregated cities in America.

ARCHIVAL (CHICAGO FILM ARCHIVES, 1966):PROTESTOR: Take a bath the next time before you come here!

ARCHIVAL (EFOOTAGE, 9-3-66):MAN: Back to the jungle you guys! Back to the jungle! Go!WOMAN: Theyre all black bastards!MAN: Dont ever come back!

ARCHIVAL (HISTORIC FILMS, 8-6-66):MARTIN LUTHER KING, JR.: I have never seen, even in Mississippi and Alabama, a mobs as hostile and as hate-filled as I have seen here in Chicago.

NARRATION: Congress had banned discrimination in employment in 1964, and in voting in 1965. But when it came to housing, there was resistance, even though government policies helped create segregated neighborhoods in the first place.

Senator Walter Mondale held hearings on housing discrimination.

WALTER MONDALE: As a young senator, no one else would touch it. They were afraid of it; so I took it. We had a witness who was really powerful there. He was a young, handsome, black naval officer. Very successful in the Navy and so he was brought down to the Pentagon in a high position there only to find out he couldnt find housing.

NARRATION: His name was Carlos Campbell.

CARLOS CAMPBELL: All I wanted was a place that was near where I worked. I spent every day, virtually 24/7 a week, looking for housing and I kept getting turned down and turned down and turned down. Thirty-nine places turned me down. Over the telephone you have space. When you get there, they dont have space. It was about what was happening to my fellow warriors, and they all had complaints about housing.

WALTER MONDALE: And there was obviously a pattern of deliberate discrimination against a young man serving his country. And I think that turned a lot of people away from the idea of discrimination.

NARRATION: But a tragic event in April 1968 created a new urgency to act.

ARCHIVAL (CBS, 4-4-68):WALTER CRONKITE: Dr. Martin Luther King, the apostle of nonviolence in the civil rights movement, has been shot to death in Memphis, Tennessee.

ARCHIVAL:NEWS REPORT: All over America the black ghettos exploded in rage and grief.

NARRATION: Seven days after Kings assassination, the Fair Housing Act was signed into law. It banned deliberate housing discrimination and obligated the government to reduce the segregation that had isolated blacks, often in vast urban housing projects.

ARCHIVAL (ABC, 7-31-70):NEWS REPORT: The world of the people who live here bears very little resemblance to the American Dream.

NARRATION: In the 1970s, George Romney, President Nixons Housing Secretary, wanted to use the law to help blacks move to the suburbs. Carlos Campbell went to work for Romney.

CARLOS CAMPBELL: He wanted to fight, he wanted to go to the suburbs and he wanted to integrate and he said you have to solve these issues in the suburbs. And the President of the United States, Richard Nixon, was not supportive.

ARCHIVAL (NIXON LIBRARY):PRESIDENT RICHARD NIXON: I believe that forced integration of the suburbs is not in the national interest.

CARLOS CAMPBELL When you cannot get the support of a president you just have to sort of, like, throw up your hands, how do we how do we deal with this?

NARRATION: 50 years after passage of the Fair Housing Act, many cities remain starkly divided by race.

CARLOS CAMPBELL: No president campaigns on the basis of affecting integrated housing, desegregating the neighborhoods.Nobody. And its a big disappointment to me.

NARRATION: During the Obama administration, communities receiving federal housing funds were ordered to draft desegregation plans or risk the loss of billions of dollars. But President Trumps Housing Secretary Ben Carson has suspended those rules until at least 2024, prompting the lawsuit to be filed against him.