Nels Anderson’s World War I Diary provides a rare glimpse into the wartime experiences of one of the most well-respected sociologists of the twentieth century, the renowned author of The Hobo (1920) and Desert Saints: The Mormon Frontier in Utah (1942). Anderson, a keen observer of people, places, and events his entire life, joined the U.S. Army in 1918 at the age of 29 and was sent to Europe to fight as part of the Allied Expeditionary Force (AEF) under General Pershing. Keeping a journal was strongly discouraged during WWI, particularly among the rank-and-file soldiers, thus Anderson’s descriptions stand as a rare gem. Furthermore, his diary is the only known account of war service during WWI by a member of the LDS Church. Anderson joined the Mormon faith after accepting the hospitality of an extended Mormon ranching family during his travels throughout the American West as a working hobo. Anderson’s accounts of the St. Mihiel and Meuse-Argonne offensives are particularly remarkable given the challenges of keeping a detailed journal amidst the chaos and suffering of the war’s Western Front. His insights into the depravity and callousness of war are buttressed with intimate human portraits of those to whom he was closest. The war years provided many formative experiences that would prove to have a lasting influence on Anderson’s views regarding the working poor, authority, and human values; this would come to bear heavily on his later work as a pioneering sociologist at the University of Chicago, where he helped establish participant observation as a research method. The many introspective entries contained in this volume will be of great interest to military historians and history buffs as well as to those in the social sciences looking to find the intellectual origins of Anderson’s later work in the burgeoning field of sociology.