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."