Light and easy

Verve Music has brief descriptions of many varieties of jazz.

Another site with a quick overview of the history of jazz by period.

Art Kane’s famous group photo with full explanations of those present.

Mark Siegel’s website has a concise history of jazz.

More depth

The early years of jazz that highlights the players.

The Chicago Jazz Archive focuses on jazz in that city.

Some details about jazz in Kansas City.

Has a year-by-year and decade-by-decade breakdown starting before 1895.

The Thelonious Monk Institute of Jazz has lesson plans for grades 5,8, & 11.  Includes lots of easy to find facts in a bunch of categories:  timeline, important firsts, musicians, glossary, style sheets, education, & more.

Along with a bit of history, this site is especially for those learning to play jazz.

Most scholarly

The Institute of Jazz Studies.

New Orleans jazz.

The pre-history of jazz, chapter 1 from a book.