When was early jazz?

The early years of the 20th century. Jazz developed out of ragtime music which in turn was an amalgam of spiritual music and military marches.

1900 to 1929

The music called Jazz was born sometime around 1895 in New Orleans. It combined elements of Ragtime, marching band music and Blues. What differentiated Jazz from these earlier styles was the widespread use of improvisation, often by more than one player at a time. Jazz represented a break from Western musical traditions, where the composer wrote a piece of music and the musicians tried to play it back exactly. Jazz tunes were just a starting point or reference for the musicians to improvise on, usually ending up with something completely different.
This total improv style began to disappear with the beginning of the big band circa 1930, after the great depression, where music began to rely on the power of the arrangers rather than the collective improvisation of the musicians in a group.

check out http://www.redhotjazzarchive.com.

yeah early 1900's for the most part. Big Bands emerge aound the 20's with Gershwin, and you have bands like Glenn MIller playing in the forties.

Let's put it this way, Louis armstrong was born in 1901.
He brought jazz from New Orleans to Chicago.
That was early jazz.