Sociologists have long argued that institutions like religion or economy can become relatively distinct spheres that facilitate and constrain action, goal setting, and decision-making. But, few empirical studies have looked closely at how institutions become relatively distinct cultural and structural domains. This paper examines how institutional entrepreneurs-in this case, Major League Baseball (MLB) sportswriters-build and sustain institutional boundaries by considering how they create a distinct cultural discourse that infuses baseball places, times, and events with culturally distinct meanings. Drawing from sportswriters' columns, documentaries, and monographs written on baseball, we show that MLB entrepreneurs have developed and disseminated a discourse oriented around the generalized medium of sport exchange, interaction, and communication: competitiveness. Using these data, the paper below examines how this medium becomes quantified and embodied in tangible and intangible forms. Additionally, the paper draws on sports columns that illustrate how MLB entrepreneurs protect the autonomy of a sacred core (the Hall of Fame) from internal threats (gambling and performance-enhancement drugs) and external corruption (the influence of money). The paper ends with a discussion of implications for the applicability of the findings to other sports and institutional domains.