As I started my research I had initially thought that jazz was just an African-American underground scene, but I quickly found out that it had originated or was born, if you will, from slavery.
After the abolition of slavery, this led to opportunities for freed African-Americans. Most who had gifts with music found work in the early “low class” entertainment business. Pianists in bars, entertainment for dances. From roughly 1900 to 1917 a predominant style of jazz was ragtime, which is defined as propulsively syncopated.
Scott Joplin who was called “King of Ragtime” published his first rag “The Maple Leaf Rag” in 1899 and later went on to publish many more such as “The Entertainer” in 1902.
In the 1920’s jazz had become the underground music of the time and played in the underground drinking clubs as dance music. Jazz was beginning to get a reputation of being immoral.
In the 1930’s Jazz was still evolving, as it always does, and the style of this time was Swing. Still dance music, but orchestrated with solos.
By the 1940’s Bebop style players began to push away from dance style music to more musician style music.
From this idea many different musicians started to push ideas but nothing really stirred until the 1950’s when free jazz came about.
Kevin Hundley 
p.s. i love your ragtime piano video.
Kevin, promising start! The introduction is well written, and it seems like you are about to launch into a thorough post on jazz history. Unfortunately, you fizzle out fairly quickly. Please add to this!