Here is a very basic history of traditional jazz music. For a more thorough account, I encourage you to visit the Red Hot Jazz site and Jazz Roots.
It is generally believed that jazz music was first played at the beginning of the last century. It was first heard in New Orleans in the Storyville District, when pianists and street bands combined European-style melodies with African-style rhythms.
This music was introduced to the rest of the country and became popular when the Original Dixieland Jazz Band recorded some of their songs on Victor records in 1917.
Other artists from New Orleans also gained immense popularity and became famous throughout the world. Ferd "Jelly Roll" Morton, Sidney Bechet, Edward "Kid" Ory, and Louis Armstrong are a few of the ones you should check out if you haven't heard of them before. The best New Orleans jazz musicians listen and learn from these great founders.
When the government closed the Storyville District in 1917, the New Orleans musicians spread throughout the country. Chicago and New York became the new centers of this music, as well as the steamboats traveling up and down the Mississippi.
At this time, the music was simply called "hot jazz." The form evolved, spreading America's classical music throughout the country. The original New Orleans music came to be known as "Dixieland". Now the players in New Orleans usually call it "traditional jazz", or just "trad" music.
Jazz music continued to grow and change. "Big bands" became the rage of the 1930's and the more complex, be-bop style evolved throughout the 1940's and 50's.
Traditional jazz also evolved and changed over the years. Oftentimes, musicians now will play the same songs that were played in 1917, but with swinging rhythms and more modern melodic lines. Brass band musicians often play the same songs in a whole different, funky way.
There are still great musicians who represent all of these different styles, and you can hear them every night here in New Orleans. I hope you will take advantage of this. Also: If you like what you hear, don't forget to contribute to their tip jars! Help keep the music alive.