The first New Orleans Jazz and Heritage Festival was held in 1970 and about 350 people attended, that time it included gospel singer Mahalia Jackson and the other 100 or so local musicians who performed.

Now four decades later, the Fest draws hundreds of thousands of fans from around the world to hear bands perform jazz, blues, country, Cajun, rap and rock.

The festival’s 40th anniversary kicks off Friday with a tribute to Jackson by Grammy-winning soul singer Irma Thomas and a performance by New Orleans native trumpeter Wynton Marsalis. This year’s headliners include Bon Jovi, Sugarland, Kings of Leon and The O’Jays.

Launching Jazz Fest in New Orleans took years, Wein said, in large part because of segregation during the early 1960s.

When the Civil Rights Act passed in 1964, the first festival was announced but later cancelled because violence and discrimination around the South continued against blacks who were trying to integrate, he said. But by 1970, things had settled.

The first Jazz Fest was held at Louis Armstrong Memorial Park and the park’s Congo Square, where in the 1800s slaves and free blacks would gather on Sundays to play music, dance, socialize and market goods. At the first festival, musicians shared four stages over two days.