The purpose of this study was to examine the life and work of Frank William Westhoff (1863-1938), a leader in music education during the progressive era (circa 1890s-1950s). Research questions focused on his work as a music supervisor, teacher educator, pedagogue, and textbook author. I also explored Westhoff's contributions to the profession and influence on music education. Westhoff was born in St. Charles County, Missouri, in 1863. He moved to Decatur, Illinois, in 1884, and in 1893 he began supervising music in the city's public schools. From 1901 to 1935, Westhoff served as music instructor at ISNU, where he taught methods classes, directed ensembles, and supervised music in the local public schools. He died in Normal, Illinois, in 1938. Although Westhoff was not as prominent a figure in music education as those who led the field on a national level during his time, he played an important role in sustaining, perpetuating, and expanding school music on a regional basis throughout much of the progressive era. He was a founding member of Music Supervisors' National Conference at Keokuk, Iowa, in 1907, and published numerous compositions and didactic materials, including a statewide curriculum that helped standardize music instruction in Illinois.