BACKGROUND: In the context of increasing cohabitation and growing demand for understanding the driving forces behind the cohabitation boom, most analyses have been carried out at a national level, not accounting for regional heterogeneity within countries. OBJECTIVE: This paper presents the geography of unmarried cohabitation in the Americas. We offer a large-scale, cross-national perspective together with small-area estimates of cohabitation. We decided to produce this map because: (i) geography unveils spatial heterogeneity and challenges explanatory frameworks that may work at the international level but have low explanatory power in regard to intra-national variation. (ii) we argue that historical pockets of cohabitation can still be identified by examining the current geography of cohabitation. (iii) our map is a first step toward understanding whether the recent increase in cohabitation is an intensification of pre-existing traditions or whether it has different roots that also imply a new geography. METHODS: Census microdata from 39 countries and 19,000 local units have been pulled together to map the prevalence of cohabitation among women. RESULTS: The results show inter- and intra-national regional contrasts. The highest rates of cohabitation are found in areas of Central America, the Caribbean, Colombia and Peru. The lowest rates are mainly found in the United States and Mexico. In all countries the spatial autocorrelation statistics indicates substantial spatial heterogeneity. CONCLUSIONS: Our results raise the question as to which forces have shaped these patterns and remind us that such forces need to be taken into account to understand recent patterns, particularly increases, in cohabitation.