Donald Cash was just a teenager in 1963 when he finished his shift at a downtown clothing store and joined the throngs marching toward the Mall.

He never got close enough to hear the Rev. Martin Luther King Jr. speak but always considered himself a beneficiary of the march as one of the first African Americans hired to cut meat at a Giant supermarket.

Now 68 and a veteran labor and civil rights activist, Cash will be walking toward the Mall again this weekend, to mark the 50th anniversary of the March on Washington, the landmark protest remembered most for King’s monumental “I Have a Dream” speech.

But the Supreme Court’s recent ruling that struck down part of the Voting Rights Act of 1965 and the stark racial divide among Americans after a Florida jury acquitted the man who fatally shot black teenager Trayvon Martin have spurred debate about how much has changed and what more there is to do.

“I had hoped when I was a young man that we’d see a lot of progress by now,” said Cash, a resident of Columbia. “But I think we’re going backwards.”

A Saturday march tracing the historic 1963 route is one of the main events of a full week of activities commemorating the march, which drew 250,000 participants. For the anniversary march, the National Park Service has issued a permit for up to 150,000 people. A second, smaller march will be held on the anniversary itself, Aug. 28.

That day, church bells will peal in communities throughout the country at 3 p.m., the moment when King began addressing the crowd. In an afternoon ceremony jointly sponsored by the Park Service, the King Center and the legacy organizations involved in the 1963 march, President Obama will speak from the steps of the Lincoln Memorial, where King stood. The first African American president will be joined by former presidents Jimmy Carter and Bill Clinton.

In many ways, the events are not purely commemorative but about unfinished business. The Saturday march is billed as a National Action to Reclaim the Dream. The march next Wednesday is called the March for Jobs and Justice.

“The message is that we still have to deal with issues that are alive in the 21st century,” said the Rev. Al Sharpton, the talk-show host whose National Action Network is co-sponsoring the Saturday march with a host of other labor and civil rights groups. “While we celebrate 50 years of progress, we still have not achieved the dream of Dr. King.”

Sharpton said that dream is not narrowly the province of African Americans.

“We’re going to make sure that representatives of the LGBT community speak at the march,” he said. The organizer of the 1963 march, Bayard Rustin, was openly gay, and some in the movement tried to push him aside.

“Women weren’t major speakers,” Sharpton said. “We’re going to correct that.”

At the moment, it is unclear how big a crowd will be drawn to Washington for the anniversary.

All 600 parking spaces for buses at RFK Stadium have sold out for Saturday, but none have been reserved for Wednesday. Several downtown hotels said that reservations are ticking up but that plenty of rooms remain available.

The kickoff event is a praise and worship service at Mount Airy Baptist Church on North Capitol Street NW, scheduled for 7 p.m. Wednesday. It is open to the public.

Conferences and panel discussions will be held by a variety of institutions throughout the week. Many events will be attended by some of the last surviving lions of the movement or their descendants.

The Southern Christian Leadership Conference (SCLC) has timed its 55th convention to coincide with the commemoration. King’s daughter Bernice will appear at the Newseum with journalist and author Simeon Booker to discuss news coverage of the civil rights movement. Myrlie Evers-Williams, the widow of Medgar Evers, will join Julian Bond and the Rev. Jesse Jackson at the A. Philip Randolph Institute.

Howard University will hold a conference on civil rights. The Historical Society of Washington has a panel discussion on the march’s impact.

Although no one doubts that progress has been made from an era when segregation was legal in much of the country, there appear to be generational differences of opinion in just how much. In a 2011 Washington Post-Kaiser Family Foundation poll, 52 percent of African Americans agest 18 to 29 said that the economic system is fair, compared with 31 percent who said it was stacked against black people. African Americans older than 50 took the opposite view, with 55 percent calling the system unfairly stacked against black people. Overall, 35 percent of African Americans said the system is equally fair, and 45 percent said it was unfair to blacks.

That is why many are calling for those celebrating the anniversary to focus on the work ahead.

“I understand the symbolism of a march,” said Van White, 51, founder of the Center for the Study of Civil and Human Rights Laws, which is based in Rochester, N.Y., and is organizing the Aug. 28 march. “But if it’s just a march, and you’re not doing anything to rectify the problems, what’s the march for?”

The SCLC, which King led, is focusing its convention on discussions of poverty and voting rights.

“Regrettably, the call for jobs and freedom echoes as much today as 50 years ago,” said Maynard Eaton, a spokesman for the group.

And that is why Ralph Worrell is coming to Washington from Atlanta. In 1963, he was a union activist who urged his fellow members to join the march. He listened to King’s speech from backstage.

Now 84, Worrell plans to work on crowd control at Saturday’s march.

“The Voting Rights Act has been taken away from us,” he said. “Immigration is important. Education is not administered throughout the country equally. These are issues that have to be addressed. We have to put the brakes on; we’re going in reverse.”

Frank Smith, chairman of the D.C. host committee, will march Saturday, too. A former D.C. Council member, Smith spent the early 1960s as a civil rights worker helping African Americans register to vote in some of the most dangerous and racist parts of Mississippi. At the 1963 march, Smith thought King was speaking directly to him when he urged participants to go back to Georgia and Mississippi and Alabama and Louisiana.

The last time he saw King was the day before he was assassinated in 1968. Smith was traveling, and while changing planes at the Memphis airport, he ran into the arriving King. The civil rights leader recognized Smith as an activist with the Student Nonviolent Coordinating Committee and suggested that he come to Memphis to organize.

Smith demurred, telling King that he was moving to Washington and might quit his work as a civil rights activist. King urged him not to, and before he turned away, spoke the last words Smith that ever heard him say:

“Don’t ever hang up your marching shoes.”

Peter Hermann contributed to this report.