Partisan polarization has been at the forefront of American politics for years. Its negative social effects seem clear, and many voters and political elites appear to agree that unchecked partisan polarization causes harm to our democratic institutions. However, it also feels like these social divisions are not on track to improve anytime soon. If most people agree that Republicans and Democrats just need to get along, then why are we still so divided by partisanship? Why did this divide emerge in the first place? And if polarization is a defining problem of American politics today, then what can be done to alleviate or at least mitigate its effects? This course will explore these questions by discussing relevant literature on American political parties, voter partisanship, and partisan polarization. By the end of the course, students will have an improved understanding of American partisanship and how it impacts many of today's most pressing policy issues.