This book is a study of soldiers who served in Irish regiments during the American Civil War and the communities that supported them. Tracing the organization and service of self-proclaimed Irish units from Connecticut, Illinois, and Wisconsin, this study transitions the historical debate away from the motivations and sentiment of “Irish America”—a national cohesive entity with similar experiences and attitudes—and towards “Irish Americas,” men and women connected to both local as well as national communities. Such an approach allows us to better understand how adopted citizens, their comrades in arms, and their friends and neighbors experienced the Civil War era. As a social history of the Civil War, Shades of Green explores the experiences, motivations, political identities, and ideologies of Union soldiers and civilians with a particular focus on the impact of the war on immigrants in smaller communities scattered throughout the North. Utilizing an array of sources including muster and descriptive rolls, federal census data, and veterans pensions, this book argues that Irish regiments were as much the expressions of local enlistment patterns as they were reflections of a commitment to a broader Irish American national identity.