Through the study of a pioneering experiment led by the Seine department from the end of the 19th century, this article shows that psychiatric assistance was never limited to the practice of institutionalization in asylums. Indeed, the creation of “colonies familiales d’aliénés” demonstrates that both alienists and public authorities sought to envision and implement other arrangements for mental health care, emancipating themselves from the rules laid out by the 1838 law on asylums well before the interwar period and the creation of the first open services. By investigating their respective goals and roles, it is possible to approach the history of French psychiatry from a medical, political and economic perspective, and to counter the view that the first years of the 20th century, characterized by an increase in institutionalization, were a time of immobility and therapeutic renouncement.