Rather endearingly, Louis Armstrong always believed he was born on the Fourth of July, 1900. It's a temptingly romantic notion; the great genius of American music, who almost single-handedly fathered a new art form, jazz, born Independence Day on the cusp of what would be in many ways the American century. The truth is more prosaic. His baptismal certificate shows that he was born in New Orleans exactly 13 months later, on this day 100 years ago.
Few could have come into the world more disadvantaged. He was black, poor and illegitimate. His parents, William Armstrong and Mary Albert, split up soon after he was baptised - "according to the rite of the Roman Catholic Church", as his certificate puts it - in the Crescent City's Sacred Heart of Jesus Church. His mother, who was about 17 when he was born, left him with his grandmother, Josephine, while she moved to Perdido Street in the heart of Storyville, the city's notorious red-light district, to work.
It's assumed she was, part-time at least, a prostitute. Certainly, when she took him back into her care when he was five, the house had a succession of "stepfathers". His own father, busily involved in a second marriage and family, was a stranger to him - a void which influenced his career later on. And when the poverty became too grinding, his mother, known as Mayann, occasionally turned tricks to feed herself, Louis and his sister, Beatrice (called Mama Lucy in the family, Beatrice was the result of a brief reconciliation between Mayann and her "husband").
The casual circumstances of his childhood were reflected in almost everything around him. Blacks went as readily to Catholic as Baptist churches; voodoo was a lively religious ingredient, too. Jobs were found wherever they could be. In an ambience where to be streetwise was a more valuable survival tool than book learning, blacks were also well down the education ladder.
Segregation was rife. Even in the legally sanctioned red-light district, the customers were white and the whores strictly separated according to colour. Where possible, sporting houses offering black prostitutes were on one side of the street, white ones on the other.
Young Louis, venturing into these surroundings to work collecting junk and delivering coal for a respectable Jewish family, the Karnoffskys, had some immunity from police harassment - but not because he was only five years old; the fact that his employers were white made him feel safer. He never forgot their kindness. Despite the deprivation, he had a warm and generous nature and responded to that quality in others.
And there was music. Everywhere. Brass bands, dance bands, small groups to entertain the sporting house clientele, little bands to advertise concerts and dances, marching bands to accompany a funeral to the cemetery and to cheer up the mourners on the way back. Surrounded by music, Armstrong's talent showed early but, given his poverty and lack of formal training, and the modest expectations they bred, it might not have flowered as it later did.
On New Year's Day, 1912, however, he was arrested for firing six blanks from the pistol of one of his "stepfathers" in Canal Street, the city's main thoroughfare. Named and shamed in the Times-Picayune, he was sent to the Colored Waifs' Home, a strict correctional institution which also had a band and a teacher, Prof Peter Davis, who began to correct some of the bad habits Armstrong had picked up on his first steps with the cornet.
Both were the making of him. By 17 he was a rising part-time musician in a city that prized music. He was also still shovelling coal. Soon after the first World War ended in 1918, in the first of four weddings, he married a prostitute, Daisy Parker. They were together a year, by which time he had been spotted by a bandleader, Fate Marable, who worked on the paddle steamers of the Streckfus line on the Mississippi.
Marable, a much sought-after schooled musician, instilled a previously lacking professionalism in Armstrong. And Armstrong, shy and shabbily dressed, very much a country hick, saw more of the world upriver as far as St Louis. He learnt to read music properly, dress better and develop some sense of what he wanted as a musician.
It wasn't the predictable, stodgy rhythms of the riverboat bands. He resigned and went back to New Orleans, where he was seen as the main challenger for the crown of Joe "King" Oliver, the top trumpeter there. When Oliver moved to Chicago, he sent for the emerging contender to join his band in 1922. There Armstrong stayed, modest as ever, even though it was soon clear he was in a different league to his boss.
The band's pianist, Lil Hardin, could see that, too. When they married, she urged him to strike out on his own. Eventually he took her advice. Typically, he went reluctantly, but his influence on a whole generation of jazz musicians was already becoming apparent. He taught them how to swing and expanded the range of the instrument, especially after he switched to the more penetrating trumpet from the mellower cornet, and drew his ideas from a well of melodic invention so great that it took years to run dry.
As with Charlie Parker a generation later, he affected the way every other instrument used in jazz was played. He burst the ensemble conventions of traditional New Orleans jazz, thrusting the improvising soloist to the forefront of the music's evolution. In this he had only one serious rival - soprano saxophonist and clarinettist Sidney Bechet, another native of the Crescent City - but when they locked horns on record in the mid-1920s there was no doubt who was the master.
His shyness gone, he was a major star in the 1930s, leading big bands whose sole raison d'Ωtre was his trumpet, gravel-voiced singing and ebullient personality. After the second World War, when economics killed most of the big bands, he returned permanently to the trumpet/trombone/clarinet New Orleans line-up of his early days. This time the emphasis of his All-Stars was on the soloists and he had some of the best, including trombonists Jack Teagarden and Trummy Young, pianist Earl Hines and clarinettists Barney Bigard and Ed Hall. His warmth and exuberance made him still the focal point. But the effervescent good humour, the handkerchief and the big smile that epitomised his unthreatening stage persona caused more politically aware later generations of African-Americans to call him an Uncle Tom.
He wasn't. For all his geniality, he was no coon caricature. His tough core of self-respect revealed itself, to everyone's astonishment, in 1957. On television, he saw a white man spit in the face of a black girl amid a school desegregation crisis in Little Rock, Arkansas. His habitual amiability deserted him. "The way they are treating my people in the South, the government can go to hell," he told a reporter, adding that "it's getting so bad a coloured man hasn't got any country". Calling President Eisenhower two-faced and gutless, he cancelled an international goodwill tour on behalf of the US.
And despite criticism from prominent establishment African-Americans such as Sammy Davis Jnr and Harlem's leading politician, Adam Clayton Powell, he wouldn't back down. In Louisiana, the law prevented integrated bands - like his All-Stars - performing in public, so he refused to play there at all. "Jazz was born there and I remember when it wasn't no crime for cats of any colour to get together and blow," he said. Something had snapped permanently in his view of the world.
How he saw that world was, however, deeply shaped by the circumstances of his early life. Interviewed by the BBC's Michael Parkinson, he could still say, seriously, that the best advice he ever got was to have a white man take care of business for him. "You need a white man to put his hand on your shoulder and say: 'This is my nigger'."
He got such a white man when the domineering Joe Glaser became his manager in the 1930s. Glaser did direct his career and keep him working - too much, according to some, who believe that it shortened his life. His estate was just over half a million dollars when he died; Glaser's was $3 million. It's a big price to pay for a father figure. Nevertheless, Armstrong was a huge influence on 20th-century popular music. Anyone who doubts this should listen to what went before him; it's like night and day, the stiff and predictable superseded by the spontaneous and flexible, the staid by the imaginative.
In the process he brought much joy to the world. When he died peacefully at home, in his sleep, in the small hours of July 6th, 1971, he was a greatly loved entertainer, one of the very few jazzmen known all over the globe. And the evidence suggests that in every aspect of his life, public and private, he was a decent, kind and honourable human being, a giver, not a taker. Of how many as gifted and successful could that be said?