The Rev. Martin Luther King, Jr. acknowledges the crowd at the Lincoln Memorial for his 'I Have a Dream' speech during the March on Washington, DC, 28 Aug 1963

Forty-five years ago Thursday, Americans listened as civil rights leader Martin Luther King, Jr. described his dream of justice and racial equality.

King delivered his now-famous "I Have a Dream" speech from the steps of the Lincoln Memorial at the end of a massive protest march through the nation's capital on August 28, 1963.  He warned that, 100 years after the end of slavery, African-Americans were still "crippled by the manacles of segregation and the chains of discrimination."

In his speech, the civil rights leader detailed the suffering caused by racism in the United States, and he warned that African-Americans would no longer put up with second-class treatment.

But the speech also was seen as an affirmation of core American values.  Vowing never to give up hope, King said he believed that "one day this nation will rise up and live out the true meaning of its creed" that all people are created equal.

At least 200,000 people marched through Washington, D.C. for the 1963 protest, called the March for Jobs and Freedom.  They listened to speeches by civil rights leaders and performances by folk musicians like Bob Dylan and Joan Baez.

One year later, Congress passed the Civil Rights Act of 1964, prohibiting segregation and re-affirming African-American voting rights.

Thursday, Barack Obama will formally accept the Democratic party's nomination for president.  Obama is the first African-American major party presidential candidate, and his speech, coming on the anniversary of King's famous address, will be closely watched.