50th anniversary of the March on Washington (49 images)

President Barack Obama and First Lady Michelle Obama wave as they leave the 50th Anniversary of the March on Washington at the Lincoln Memorial in Washington, D.C. on August 28, 2013. Thousands gathered at the Memorial to celebrate the anniversary of Martin Luther King Jr.'s "I Have a Dream" speech. UPI/Kevin Dietsch

A crowd gathers to hear US President Barack Obama (not pictured) deliver remarks during the 'Let Freedom Ring' commemoration event, at the Lincoln Memorial in Washington, DC on August 28, 2013. The event was held to commemorate the 50th anniversary of the August 28, 1963 March on Washington led by the late Dr. Martin Luther King Jr., where he famously gave his 'I Have a Dream' speech. UPI/Michael Reynolds

US President Barack Obama (front R), First Lady Michelle Obama (front L), former US President Jimmy Carter (back L) and former US President Bill Clinton (back R) walk down the steps of the Lincoln Memorial to attend the 'Let Freedom Ring' commemoration event, in Washington, DC on August 28, 2013. The event was held to commemorate the 50th anniversary of the August 28, 1963 March on Washington led by the late Dr. Martin Luther King Jr., where he famously gave his 'I Have a Dream' speech. UPI/Michael Reynolds

US President Barack Obama delivers remarks during the 'Let Freedom Ring' commemoration event, at the Lincoln Memorial in Washington, DC on August 28, 2013. The event was held to commemorate the 50th anniversary of the August 28, 1963 March on Washington led by the late Dr. Martin Luther King Jr., where he famously gave his 'I Have a Dream' speech. UPI/Michael Reynolds