<!doctype html public «-//w3c//dtd html 4.0 transitional//en»> http-equiv=content-type> This study investigates the long history of American conspiracy theories. Whereas most extant research claims that conspiracy theories have never been more widespread and influential than in the present, the book demonstrates that the opposite is the case. Until far into the twentieth century, conspiracy theories were considered a perfectly legitimate form of knowledge. They shaped how many Americans understood and reacted to historical events.