Celebrations commemorate Martin Luther King Jr's historic speech
The week of commemorations in Washington will culminate on August 28, when President Barack Obama, the first black US president, will speak at the Lincoln Memorial 50 years to the day after King made his historic address at the site.
King, an advocate of non-violence, was among six organisers of the 1963 March on Washington, a rally for jobs and freedom. King led about 250 000 marchers to the Lincoln Memorial on the National Mall and delivered his signature "I Have a Dream" speech from its steps.
The March on Washington helped pressure Congress to pass the landmark Civil Rights and Voting Rights acts in 1964 and 1965, respectively. The Supreme Court struck down a key provision of the Voting Rights Act in June, and Obama has called that ruling a setback.
King was awarded the Nobel Peace Prize in 1964.
A white drifter assassinated him in 1968 at age 39.
Events in Washington will kick off on Wednesday with a commemorative service at Mount Airy Baptist Church. Seminars on women and young people in the civil rights movement and on March on Washington figures Bayard Rustin and A Philip Randolph will take place in the following days.
Civil rights groups the National Urban League and King's Southern Christian Leadership Conference (SCLC) will also be holding events in Washington. The SCLC's international convention on Friday will feature debates on race and poverty and on voting rights.
Civil rights-related events
The US Postal Service will unveil a commemorative stamp on Friday, and a Sunday gospel brunch with opera singer Denyce Graves is tap. The National Park Service has scheduled numerous civil rights-related events on the National Mall.
The Smithsonian Institution has an exhibition at the National Museum of American History commemorating the 1963 march and the 1863 Emancipation Proclamation by President Abraham Lincoln, complete with Lincoln's stovepipe hat.
The Smithsonian is holding a concert and a mock training session for participants in a desegregation sit-in, and is releasing a playlist of music from the civil rights movement. The National Portrait Gallery also has a show on King and his life.
The Newseum, a museum dedicated to US media, started exhibits this month highlighting the role of students in the civil rights movement. They include a section of retailer FW Woolworth's lunch counter where North Carolina students started sit-ins in 1960.
On Saturday, some 100 000 people are expected at a march on Washington's National Mall organised by civil rights leader and TV commentator Al Sharpton and by King's oldest son. The National Action to Realise the Dream march will group unions, civil rights and Hispanic groups and Democratic political leaders.
Family of Trayvon Martin
The march is focused on a host of issues, including jobs, voting rights, gun violence, women's rights and immigration. Speakers include the family of Trayvon Martin, the black Florida teenager shot dead by a volunteer watchman, and Georgia Democratic Representative John Lewis, the last surviving organiser of the 1963 march.
The Let Freedom Ring ceremony at which Obama will speak on August 28 will include speeches by former presidents Jimmy Carter and Bill Clinton, both Southern Democrats. The commemoration will include the ringing of bells at dozens of US sites at 3pm (1900 GMT), the time when King delivered his address.
Outside the United States, bell-ringing is also scheduled at sites including Katmandu, London and Tokyo, all at 3pm local time, according to Atlanta's King Centre, which is among the organisers of many of the commemorative events. – Reuters