Americans across the political spectrum have come to live by a pervasive belief that the world is a dangerous place and that our nation, and ourselves, are at risk of invasion and attack. Deeply ingrained attitudes, political developments, and public policies have heightened that sense of vulnerability, and also fostered widespread agreement that individuals are responsible for their own protection. This lecture explores how and why that culture of security emerged, how it has changed over time, and its impact on how Americans pursue their daily lives, act politically, and relate to each other. We are left wondering, are we any safer as a result of all the effort poured into achieving security? What have we gained — and what have we lost?