Former US President Bill Clinton attended a ceremony in Arkansas to mark 50 years since an integration crisis at Little Rock Central High School.
The crisis lasted for three weeks in 1957, as an angry mob tried to stop a group of nine black students attending the all-white school.
The confrontation was only ended when former President Dwight D Eisenhower sent in troops to control the crowds.
The event became a seminal moment in the civil rights movement in the US.
The anniversary comes a week after thousands marched through the town of Jena, Louisiana to protest about allegations of unequal racial justice in a case which has seen several black high-school children jailed.
In Little Rock, about 4,500 people gathered in front of the Central High School on Tuesday to honour the bravery of the group of black teenagers – now in their sixties – who have become known as the “Little Rock Nine”.
Mr Clinton, a former governor of Arkansas, held open the school’s doors in a symbolic gesture.
|You can overcome adversity if you know you are doing the right thing
Carlotta Walls Lanier
Member of the Little Rock Nine
“I am grateful we had a Supreme Court that saw ‘separate but equal’ and ‘states’ rights’ for the shams they were, hiding our desire to preserve the oppression of African-Americans,” he said.
“I am grateful more than I can say that we had a president who was determined to enforce the order of the court.”
One of the nine, Carlotta Walls Lanier, urged the school’s current generation of students to have the courage to act on their convictions.
“You can overcome adversity if you know you are doing the right thing,” she said.
Another, Ernest Green, said the group had believed the school was “the place that would accept us, that we’d belong”.
“We saw it as a building that offered opportunity and options for us. And you know what? Fifty years later, I think we were right,” he told the crowd.
On reaching the school gates, she was blocked by a member of the Arkansas National Guard.
They had been stationed there by Arkansas Governor Orval Faubus as part of a campaign of “massive resistance” to a 1954 Supreme Court ruling that segregated classrooms were unconstitutional.
Ms Eckford was later joined by eight other pupils.
The confrontation at the school quickly escalated into a showdown between the state and the federal government.
President Eisenhower eventually sent in troops from the 101st Airborne division to escort the group to class on 25 September 1957, dealing a crushing blow to opponents of the black civil rights movement.
Story from BBC NEWS: