Nonprofit boards, as boundary spanners, often serve the institutional purpose of affording legitimacy to organizations. Neo-institutional theory suggests that nonprofit organizations, as particularly susceptible to legitimacy demands of changing environments, would tend toward rationalizing internal structures. This article, using historical panel data, explores the extent of one form of rationalization, recruiting trustees with college education and/or professional or managerial occupations. It finds that trustees with college education, managers, and professionals continue to have significant representation on nonprofit boards. Also, many boards are increasingly less exclusive with respect to gender, race, and religion. Some select nonprofit boards, however, continue to be dominated by different gender, racial, and religious identities, suggesting that nonprofit boards also serve the purpose of representing different identity and/or interest groups in the community.