Moving away slightly from the linear movement of jazz from New Orleans to Chicago, I think it would be important to look at a number of people and events that were happening in New York City prior to the 1920's. James Reese Europe was at the forefront of early jazz, although, parodoxically, it wasn't technically jazz music that his band played. However his work with Vernon and Irene Castle helped to establish the notion of "acceptable" dancing behaviour in American society. This cannot be overlooked. As mentioned in a previous entry, American and British societies were heavily constrained by Victorian morals and values. The idea of a couple dancing something like the foxtrot would have been abbhorant to a lot of people in the late 19th century. (This is the era where even the legs of stools and pianos were deliberately covered up!)The Castles approach to dancing changed all that. And as jazz is essentially "dance" music then it was only natural that people sought to hear this new form of music.
James Reese Europe
Vernon & Irene Castle
Europe's career was brief. He did record with his band as early as 1914, however they are not regarded as jazz records as such. He later did record a number of dixieland standards after he returned from World War I, including St Louis Blues and Memphis Blues. He was also innovative in introducing the saxophone into the line up. Until then it was regarded as something of a novelty instrument.