The jíbaro—the emblematic figure of Puerto Rico—has long been at the center of the archipelago’s political and professional discussions. Building on the work of scholars who have traced the jíbaro’s history, this article complicates the tension between the politically nationalistic definition of humble jíbaros working in the countryside and scientific observations of jíbaros within the confines of the criminal-legal system. By the mid twentieth century, mainstream understandings of jíbaros were increasingly fashioned by psychiatry, social science, and social work, all of which connected jíbaros to other rural identities. These projections of the jíbaro powerfully materialized in Puerto Rico’s premier biosocial laboratory, the Insular Penitentiary at Río Piedras (popularly known as Oso Blanco). An analysis of the work of penitentiary psychiatrists and social health professionals with prison inmates reveals a more complex, troubling image of redeemable Puerto Rican men with rural roots and sensibilities than the idyllic representations of jíbaros circulating at the time suggest. Oso Blanco health practitioners pathologized the jíbaro to identify and mend his perceived psychosocial shortcomings, and to diminish any defiance he harbored. In so doing, they reinforced the notion that jíbaros were racialized living artifacts central to colonial-populist designs and constituency-building.