What is the history of Plone?
What is the history of Plone? When did it start?
Plone was an idea that started maturing in late 1999, and had its first release in 2001, and has been rapidly gaining friends around the world since then.
For a complete treatise on Plone, its history and the people involved, a good starting point is Martin Aspeli's dissertation Plone: A model of a mature open source project.