The mission at Fort Campbell has changed over the past seventy-five years, and the city has grown and adapted to meet new challenges. It was conceived before Pearl Harbor as the Tennessee-Kentucky Armor Camp and has progressed in recent years to meet changing national security needs and the transformation of the U.S. Army. The fort is home to the army's most elite air assault and airborne units. It is also the largest employer in Tennessee and Kentucky and puts $2.6 billion into the local economy each year. Author and post historian John O'Brien details the historic ride that took Fort Campbell from a Giant Bachelor City to a World-Class Army Home. John J. O'Brien retired from a twenty-year active duty military career as a lieutenant colonel of infantry. He is currently an army historian assigned as the installation historian at Fort Campbell, Kentucky. He has a BA in government, an MA in political science, an MMAS in military theory and history from the Command and General Staff College and School of Advanced Military Studies, and is a doctoral candidate in U.S. history at Saint Louis University.