The Simulmatics Corporation, founded in 1959, mined data, targeted voters, accelerated news, manipulated consumers, destabilized politics and disordered knowledge - decades before Facebook, Google, Amazon and Cambridge Analytica. Developing a ‘People Machine’, they predicted and influenced human behaviour for the presidential campaigns of Eisenhower and Kennedy, the New York Times, Mad Men ad firms and, most shockingly, the strategy of the Vietnam War. In If Then, bestselling historian Jill Lepore unearths the barely believable story of this long-vanished corporation, and of the women and men hidden behind it.