Americans today "know" that a majority of the population supports the death penalty, that half of all marriages end in divorce, and that four out of five prefer a particular brand of toothpaste. But remarkably, such data - now woven into our social fabric - became common currency only in the last century. Sarah Igo tells the story, for the first time, of how opinion polls, man-in-the-street interviews, sex surveys, community studies, and consumer research transformed the United States public.