In this wide-ranging and innovative study, Keith T. Poole and Howard Rosenthal use 200 years of congressional roll call voting as a framework for a new interpretation of important episodes in American political and economic history. Despite the wide array of issues faced by legislators over the past two hundred years, the authors have found that over eighty percent of a legislator's voting decisions can be attributed to a consistent and predictable ideological position ranging from ultraliberalism to ultraconservatism. Using a simple geometric model of voting, the authors shows that roll call voting has a very simple structure and for most of American history roll call voting patterns are very stable. This stability is based upon two great issues - the extent of government regulation or intervention in the economy, and race. Poole and Rosenthal also examine alternative models of roll call voting and find them lacking. In several detailed case studies, they show that constituency interest or pocketbook voting models fail to account for voting on minimum wages, strip mining, food stamps, and railroad regulation. Because of its scope and controversial findings which challenge established political and economic models used to explain Congressional behavior, Congress will be essential reading for both political scientists, economists, and historians.