I've continued to mull over the question of whether jazz evolved all over the slaveholding south, or specifically and exclusively in New Orleans.

I've come to the conclusion that the blues, and ragtime, and American "roots" music in general, did indeed develop all over the place, wherever African-Americans and European-Americans made music together, or even influenced each other's music indirectly.

Jazz, however ~ the original group-improvisation genre first known as jass/jazz and now recognized as "trad-jazz" and/or "dixieland" ~ DID develop in New Orleans.