If you were asked when America became polarized, your answer would vary depending on your age. For leading historians Kevin Kruse and Julian Zelizer, it all starts in 1974. In that one year, the nation was rocked by one major event after another.
In terms of politics and economics, in their cultural and social relations, Americans have recently discovered we actually share little common ground with one another. How did we get here?
In their new book, "Fault Lines," Kruse and Zelizer examine the persistent development of political, economic, racial, religious and sexual divisions in modern America, as well as the cultural and technological changes that fostered and evolved from such divisions.