The eco-museum of Saint-Quentin-en-Yvelines was amongst the first ten eco-museums created in France. It is characteristic of a militant approach to culture in which the population is central to the museal project. The museum is associated with the emergence of the new town and comes within the process of community initiatives wanted by the town-planners. Concerned both with the past and with the mutations induced by the town construction, it is confronted with complex and political problems raised by an imposed “inter-communality” and becomes a tool of “memory” that various categories of actors try to appropriate. This atypical museum must develop an interdisciplinary research policy and pioneer the acquisition of collections on urban ways of life so as to be able to testify to a history and a heritage which are still too new to get a legitimate status.