Why do secular states pursue substantially different policies toward religion? The United States, France, and Turkey are secular states that lack any official religion and have legal systems free from religious control. The French and Turkish states have banned students' headscarves in public schools, whereas the U.S. has allowed students to wear religious symbols and attire. Using the method of process tracing, the author argues that state policies toward religion are the result of ideological struggles. In France and Turkey the dominant ideology is "assertive secularism," which aims to exclude religion from the public sphere, while in the U.S., it is "passive secularism," which tolerates public visibility of religion. Whether assertive or passive secularism became dominant in a particular case was the result of the particular historical conditions during the secular state-building period, especially the presence or absence of an ancien régime based on a marriage of monarchy and hegemonic religion.