Most accounts of Jazz start with a city and a date: New Orleans, around 1900. They rarely linger on the obvious follow-up. Why there? The American South was not short of Black musicians or brass bands, and yet the new music crystallized in this one port, not in any of the larger Southern cities upriver.

Nineteenth-century New Orleans was an anomaly. Founded by the French, ceded to Spain, sold by Napoleon to the USA in 1803, it inherited Catholic and Latin habits that the rest of the Protestant South did not share. The most consequential of those habits was a tolerated middle class of mixed-race Creoles, many of them free, many of them educated, many of them musically literate in the European sense.

This middle layer is the part of the story usually skipped. Creoles taught their children to read opera scores and play church organ. They also lived close enough to formerly enslaved African Americans that the drum patterns of the West African diaspora were not foreign sounds. In no other American city of the period did the European written score and the African drum sit so plainly side by side.

At the edge of the old city, just beyond the ramparts, was a patch of ground the locals called Congo Square. From the early 1800s until roughly the 1850s — an 1856 ordinance made it unlawful to beat a drum or blow a horn in the city — enslaved and later free Black residents were permitted to gather there on Sunday afternoons to drum, sing and dance. By the time the sanctioned gatherings died out, generations of New Orleanians had heard West African polyrhythm in the open air, in a way no other American city allowed.

A few blocks away, white and Creole bands rehearsed European marches. Brass-band funerals were already a New Orleans ritual: a slow dirge to the cemetery, a faster, looser march on the way home. Catholic processions, opera at the French-language theaters, work songs from the levees, and the hymns of African American churches all crowded the same dozen square miles. Nowhere else did so many kinds of music share a single neighborhood.

Around 1900, a cornet player named Buddy Bolden began stitching these strands together: blues phrasing improvised over a brass-band lineup. No recording of Bolden survives, but the witnesses are consistent. What he was playing did not yet have a name. It would acquire the name Jazz within a decade or so, by the late 1910s.

Not a second of Bolden survives, so the earliest thing we can actually play is from three decades later, when Jazz had hardened into a global popular form. Duke Ellington — who never lived in New Orleans — gave it its most quoted line in 1932: it don't mean a thing if it ain't got that swing. Ellington handed the city an unintended tribute, a nod to the improvisational pulse the New Orleans players had carried out of it.

In the summer of 1922, a 20-year-old cornet player named Louis Armstrong boarded a northbound train. King Oliver had sent for him from Chicago to join his Creole Jazz Band. Armstrong was already one of the most talented young cornetists in New Orleans; within a few years of arriving in Chicago, he would be among the most celebrated and influential players in the country.

By then Jazz had stopped being a regional music. The Mississippi was the obvious metaphor — Memphis, St. Louis, Chicago, all upriver, all hungry for the new sound — but radio, race records and the touring circuit moved faster than the boats. By the 1930s Jazz was being broadcast across Europe. By the 1950s the US State Department was sending Jazz musicians abroad as cultural ambassadors. A music born in a segregated Gulf-coast port had become, within a few decades, the very thing America chose to show the world.

The track below is Armstrong forty-five years after he left the city, in 1967, on the song most people who have never bought a Jazz record can still hum. The cornet he learned in New Orleans funeral parades is gone. What returns instead is his voice — graveled, plain, recognizable from a single syllable.

Walk through the French Quarter today and you will still hear a cornet from a doorway by sundown. The city has not stopped being a Jazz city. But what you hear now is more a tourist memory of the music than the working sound it was in 1905.

To say Jazz was born in New Orleans is half right. The other half is that the music was already preparing to leave the moment it was born. A sound that needed a Creole port and a Sunday drumming square to be invented turned out to need neither to survive. Within fifty years of Buddy Bolden picking up a cornet, the world was speaking the language he had been improvising on a Louisiana street corner.