Impetus behind SOPA/PIPA

Regarding the current flare up over those two Congressional/Senatorial bills, can anyone provide a detailed summary of when and why those two bills were proposed in the first place? IE a factual timeline of the causes behind it.

Instead of going dark today, Ars Technica is using SOPA Resistance Day to devote all its articles to coverage of the issue. They’ve been consistently good in their coverage (especially since they are staunchly in favor of defending copyright). A good start on the bill’s history is this article on the sponsors.