World War I propelled the United States into the twentieth century and served as a powerful catalyst for the making of modern California. The war expanded the role of the government and enlarged the presence of private citizens’ associations. Never before had so many Californians taken such a dynamic part in community, state, national, and international affairs. These definitive events unfold in California at War as a complex, richly detailed historical narrative. Historian Diane M. T. North not only writes about the transformative battlefield and nursing experiences of ordinary Californians, but also documents how daily life changed for everyone on the home front—factory and farm workers, housewives and children, pacifists and politicians. Even before the United States entered the war, California’s economy flourished because its industrialized agriculture helped feed British troops. The war provided a boost to the faltering Hollywood film industry and increased the military’s presence through the addition of Army and Navy training camps and air fields, ship construction, contracts to local businesses, coastal defenses, and university-sponsored scientific research. In these stories, North traces the roots of California’s global stature. The war united Californians in common humanitarian goals as they supported war-related charities, funded the nation’s war machine, conserved food, and enforced rationing. Most citizens embraced wartime restrictions with patriotic zeal and did not foresee the retreat into suspicion, loyalty oaths, and unwarranted surveillance, all of which set the stage for the beginnings of the modern security state. California at War raises important questions about what happens when a nation goes to war. This book illuminates the legacy of World War I for all Americans.