TheatreHistory.com
Theatre History: American Musical Theatre: An Introduction
A commercial website that provides a solid history of American musical theatre. Includes summaries of many musicals through history. Focus is on shows before 1960.
Musicals 101
Musicals101: History of the Stage Musical 1910 1920
From Jerome Kern's Americanized shows to the Ziegfeld Follies, the stages saw a whole new type of musical from 1910-1920.
Musicals 101
Musicals 101: Florenz Ziegfeld
This site from Musicals 101 provides great biographical information on Florenz Ziegfeld. The text is in-depth with pictures included, and covers not only Ziegfeld's life, but also Anna Held, and the birth of Ziegeld's Follies.