In the twentieth century, hundreds of thousands of migrants seeking economic opportunities relocated from the Appalachian region to southwestern Ohio. They brought mountain and gospel music with them, as well as an openness to new sounds that were emerging in mid-century. Without access to capital, formal instruction, or mainstream media attention, a core of devoted musicians and entrepreneurs built an unrivaled radio, recording, and performance infrastructure for bluegrass music. Between 1947 and 1989, important careers were launched and the distinct artistry of bluegrass made during those years in Cincinnati, Dayton, Middletown, Hamilton, Springfield and environs—an area of approximately 250 square miles—had a permanent influence on American roots music. This work explores the history of southwestern Ohio’s Appalachian migration and the subsequent proliferation of bluegrass musicians, radio broadcasters, recording studios, record labels, bars, festivals, and sacred music. It also explores how following generations built upon that base, how bluegrass reached non-Appalachian participants, how bluegrass was used in public education and community development, and how distinctive musical qualities of bluegrass that flourished in the southwestern Ohio region influenced the worldwide development of the genre. First-person narratives of key figures are included as well as analytical essays by academic and independent scholars, along with suggestions for further reading and listening.