If you've ever driven into the heart of Philadelphia down Lancaster Avenue, you've seen it at the big airy intersection with 40th Street -- the stark, towering mural of Dr. Martin Luther King Jr., framed like a Polaroid picture, waving from the stage to a sea of sardine-packed humanity. It depicts an event that was called the "Freedom Now" rally, which happened exactly 50 years ago today.

I wrote about that rally, as well as another memorable speech that that King gave the following day in front of the "Berlin Wall" of the then-still-segregated Girard College, and how MLK's visit affected the city and the people who saw in the Daily News last week. You can read my story here.

Despite the problems facing blacks -- in Philadelphia, and around the nation -- in 1965, there was something of an air of a victory tour for King's "Freedom Now" rallies, which hit a number of Northern cities during what became the long. hot summer of that year. In less than a year's time before King rallied in Mantua, the civil rights leader had won the Nobel Peace Prize and led the legendary Selma-to-Montgomery march; in just a few days (Aug. 6, 1965),  he would stand next to then-President Lyndon Johnson as he signed the Voting Rights Act, the second major piece of civil rights legislation in just two years.

Now, King was looking to see if the method of non-violent protest that he'd pioneered across the once-segregated South would work on the related yet more complicated problems of the inner cities up North -- poverty and unemployment, housing discrimination, unequal school and police brutality. And yet his underlying message to Philadelphia was also a deeply spiritual one. "I come here from the front lines of the civil-rights movement in the South to tell you, 'You are somebody.' Let us have a sense of somebodiness. Don't let anybody make you think that you are not somebody."

To say what happened next was a mixed bag would be a gross understatement. Integrated school and workplaces opened up new opportunities for African-Americans, and both the Voting Rights Act and black political empowerment movements led to a surge in black elected officials, culminating with the 2008 election of President Obama. But violence -- "as American as cherry pie," the black radical H. Rap Brown said famously -- claimed King's life less than three years after the "Freedom Now" rally, and urban uprisings including Watts, which erupted just nine days after the rally at 40th and Lancaster, left scars that persist a half-century later. The main problems that King addressed here in 1965 -- economic despair, unofficial segregation or disparities in schools and residential living, unjust police practices -- still exist in some form in 2015.

And then there's voting.

This weekend, the New York Times Magazine carried a remarkable article to mark the 50th anniversary of the landmark voting law. It chronicled how what should have been a triumphant moment in American social progress has instead been hijacked -- turned on its head by the forces of reaction. The piece shows how the conservative movement attacked the fundamental premise of the law and now has succeeded in many states by rolling back its most positive outcomes, such as early voting or steps that make it easier for folks to register. Here's an excerpt:

State Senator Josh Stein was sitting in his kitchen in Raleigh when the email with the new [2013 North Carolina voting] legislation came through. "My jaw hit the table," he recalled. He quickly understood what Apadoca had meant. The bill had grown to 57 pages from 14, with 48 additional sections that cut the state's early-voting period nearly in half, taking away one of the two Sundays when black churches run highly effective "souls to the polls" voting drives. It ended same-day registration and invalidated student IDs for voting. In its one act designed to improve voter access, the bill made it easier to vote by absentee ballot. None of this could have been approved under Section 5 [a critical section of the 1965 Voting Rights Act struck down by the John Roberts Supreme Court]. The email indicated that the Rules Committee would vote the following morning.

The bill alarmed North Carolina's black legislators, some of whom had worked for decades to make the state a model for inclusive voting law. They saw in it a reflection of the failed Reconstruction years. "History has a way of repeating itself," said Representative Henry Michaux Jr., who joined the North Carolina General Assembly in 1972, "and that's exactly what's happening here."

Indeed, this very 50th-anniversary week, a federal court is hearing the NAACP's legal challenge to the 2013 North Carolina law. What goes around, comes around.

On one hot August afternoon in 1965 at 40th and Lancaster, it must have felt that the arc of the moral universe would keep bending toward justice, faster and faster, with the promised land clearly in sight. But folks probably should have known better. In 1865, after all, the end of slavery and the voting promises of the looming 15th Amendment instead gave way to Jim Crow laws and lynchings. Since 1965, victories by King and the civil rights movement have been under assault -- by mass incarceration in the name of a "war on drugs, an education regime that ensures unequal schools, and by well-funded lawyers from right-wing think tanks citing a "voter fraud" problem that never existed inthe first place.

Human progress, it turns out, is not the straight line we wanted it to be. It's a spiral -- a hard, heavy spiral, weighed down by tides of repression that surge into any opening that presents itself. If Dr. King could return to that Philadelphia street corner today, I have to think he'd be discouraged by the persistence of injustice -- discouraged, but not depressed. He'd simply change into his walking boots for the next mile of the never-ending quest, for freedom now.