Book excerpt: The Road to Inequality shows how policies that shape geographic space change our politics, focusing on the effects of the largest public works project in American history: the federal highway system. For decades, federally subsidized highways have selectively facilitated migration into fast-growing suburbs, producing an increasingly non-urban Republican electorate. This book examines the highway programs' policy origins at the national level and traces how these intersected with local politics and interests to facilitate complex, mutually-reinforcing processes that have shaped America's growing urban-suburban divide and, with it, the politics of metropolitan public investment. As Americans have become more polarized on urban-suburban lines, attitudes towards transportation policy - a once quintessentially 'local' and non-partisan policy area - are now themselves driven by partisanship, endangering investments in metropolitan programs that provide access to opportunity for millions of Americans.