The article examines the invention and development of the National Day of Mourning as a counter-tradition to Thanksgiving and its “conservative” civil religious symbolism during the late 1960s and 1970s. As part of the liturgical calendar of the American civil religion, the “First Thanksgiving” is strongly anchored in the nation’s memory. However, this civil religious myth of intercultural harmony has been increasingly questioned since the Red Power movement. Overall, the National Day of Mourning is a powerful example of the political potential of holidays, of competing interpretations and functions of civil religion, as well as of negotiating memory and identities in a multicultural society such as the United States.