In the past century, the Netherlands’ nonprofit sector has grown tremendously. Nowadays, it is one of the largest in the world. This article considers the growth of the sector in general, and pays special attention to its main domains: education, health care, social work, the arts, and culture. It argues that three factors explain the sector’s current size. First, the Netherlands has a long and rich tradition of private initiatives, ranging from the medieval guilds and church-related activities to pillarization in the 19th and 20th centuries. Second, the posture of the government created a political environment that stimulated nonprofit growth. Finally, the crucial factor in the expansion of the nonprofit sector is the scheme of collective finance and private provision for key welfare state services. This scheme started ineducation and later spread to health care and social services.