For decades the American School Counselor Association has recommended that schools employ one counselor for every 250 students, but there is limited evidence the policy promotes student success. This article investigates the origins of the 60-year-old recommendation, examining how and why it has persisted. Drawing on historical documents, it reconstructs how the 250 number was derived during the 1950s and then uses a framework of institutionalization within organizational fields to explain how the ratio became cemented within and beyond the counseling field. By highlighting how the 250-to-1 recommendation is an anachronism, this article raises questions about its continued relevance.