Background: The notion that increasing prevalence of cohabitation relative to marriage, and increasing age at first marriage are part of a broader shift in societal norms — a second demographic transition — is now well supported by studies focused on US and European populations. Recent research points to the similarly high prevalence of cohabitation in Latin America as perhaps signaling the diffusion of modern ideals and norms about union formation. In Central America this is unlikely to be the case given the long history and enduring acceptance of cohabitation that is unrelated to modern ideals. While there are studies that have documented this history and current prevalence, there is no research examining the intersecting life course pathways from adolescence through early adulthood that lead to marriage or cohabitation. This is not surprising given that available data for Central American countries are not ideally suited to studying the process