ชาวอเมริกันร่วมระลึกถึงสุนทรพจน์ของมาร์ติน ลูเธอร์ คิง ในโอกาสครบรอบ 50 ปี

A tourist points to the exact location where Rev. Martin Luther King Jr., gave his famous 'I Have a Dream' speech, at the Lincoln Memorial in Washington, Aug. 22, 2013.

Rev. Al Sharpton (2nd R) links arms with Rep. John Lewis (D-GA) next to Martin Luther King III (R) as they begin to march during the 50th anniversary of the 1963 March on Washington for Jobs and Freedom at the Lincoln Memorial in Washington, Aug. 24, 2013

Crowds rally at the Lincoln Memorial in Washington to commemorate the 50th anniversary of the 1963 March on Washington, Aug. 24, 2013.

Marchers gather along the reflecting pool on the National Mall during the 50th anniversary of the 1963 March on Washington for Jobs and Freedom at the Lincoln Memorial in Washington Aug. 24, 2013.

Rev. Bobby Turner or Columbus, Ohio, places his hand on the Martin Luther King Jr. Memorial, Aug. 22, 2013, in Washington.

A marcher holds an U.S. flag bearing the image of President Barack Obama during the 50th anniversary of the 1963 March on Washington for Jobs and Freedom at the Lincoln Memorial in Washington Aug. 24, 2013.

Crowds line the Reflecting Pool to watch the 50th anniversary ceremony of the 1963 March on Washington ceremony, with the Washington Monument in the backround, Aug. 24, 2013.

U.S. Park Police watch over the Lincoln Memorial during sunrise early in the morning before the start of the ceremony honoring the 50th anniversary of the 1963 March on Washington, Aug. 24, 2013.

Marchers file towards their seats at the ceremony at the Lincoln Memorial honoring the 50th anniversary of the 1963 March on Washington, Aug. 24, 2013.

Marchers pose for pictures as they commemorate the 50th anniversary of the 1963 March on Washington for Jobs and Freedom at the Lincoln Memorial in Washington, Aug. 24, 2013.

A marcher holds a sign as she attends the 50th anniversary of the 1963 March on Washington for Jobs and Freedom at the Lincoln Memorial in Washington, Aug. 24, 2013.

The Martin Luther King Jr. Memorial in Washington, Aug. 22, 2013.

Dr. Martin Luther King Jr. acknowledges the crowd at the Lincoln Memorial for his "I Have a Dream" speech during the March on Washington, D.C. in this Aug. 28, 1963 file photo.