Barack Obama on Thursday praised the civil rights legacy of former President Lyndon B. Johnson, saying his 1960s pursuit of equality helped clear the way for an African-American to one day become U.S. president.

Obama was joined by three former presidents this week in commemorating the 50th anniversary of the passage of the Civil Rights Act of 1964, the landmark legislation that tested Johnson's vaunted negotiating skills and took a step toward ending America's segregationist past.

Speaking to a crowd at the Lyndon Baines Johnson Presidential Library, Obama lauded the 36th U.S. president's civil rights push as "one giant man's remarkable efforts to make real the promise of our founding: 'We hold these truths to be self-evident, that all men are created equal.' "