State legislatures are tasked with drawing state and federal districts and administering election law, among many other responsibilities. Yet state legislatures are themselves gerrymandered. This book examines how, why, and with what consequences, drawing on an original dataset of ninety-five state legislative maps from before and after 2011 redistricting. Identifying the institutional, political, and geographic determinants of gerrymandering, the authors find that Republican gerrymandering increased dramatically after the 2011 redistricting and bias was most extreme in states with racial segregation where Republicans drew the maps. This bias has had long-term consequences. For instance, states with the most extreme Republican gerrymandering were more likely to pass laws that restricted voting rights and undermined public health, and they were less likely to respond to COVID-19. The authors examine the implications for American democracy and for the balance of power between federal and state government; they also offer empirically grounded recommendations for reform.