In the spring of 1970, something great happened in New Orleans: musical history was made.

Four stages, a gospel tent and a few food and crafts booths were set up in Congo Square, the area adjacent to the Municipal Auditorium on Rampart Street in what is now Louis Armstrong Park. Mahalia Jackson sang “Just a Closer Walk With Thee,” Cajun musicians fiddled, Woody Allen flew in from filming Bananas to play clarinet with veteran New Orleans jazzmen led by trumpeter Punch Miller, gospe...