In recent months, medical institutions across the United States redoubled their efforts to examine the history of race and racism in medicine, in classrooms, in research, and in clinical practice. In this essay, I explore the history of racialization of the spirometer, a widely used instrument in pulmonary medicine to diagnose respiratory diseases and to assess eligibility for compensation. Beginning with Thomas Jefferson, who first noted racial difference in what he referred to as "pulmonary dysfunction," to the current moment in clinical medicine, I interrogate the history of the idea of "correcting" for race and how researchers explained difference. To explore how race correction became normative, initially just for people labeled "black," I examine visible and invisible racialized processes in scientific practice. Over more than two centuries, as ideas of innate difference hardened, few questioned the conceptual underpinnings of race correction in medicine. At a moment when "race norming" is under investigation throughout medicine, it is essential to rethink race correction of spirometric measurements, whether enacted through the use of a correction factor or through the use of population-specific standards. Historical analysis is central to these efforts.