BACKGROUND As the incidence of cohabitation has been rising in many parts of the world, efforts to determine the forces driving the cohabitation boom have also been intensifying. But most of the analyses of this issue conducted so far were carried out at a national level, and did not account 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 created this map for several reasons. (i) First, our examination of the geography of cohabitation reveals considerable spatial heterogeneity, and challenges the explanatory frameworks which may work at the international level, but which have low explanatory power with regard to intra-national variation. (ii) Second, we argue that historical pockets of cohabitation can still be identified by examining the current geography of cohabitation. (iii) Finally, our map serves as an initial step in efforts to determine whether the recent increase in cohabitation is an intensification of pre-existing traditions, or whether it has different roots that suggest that a new geography may be evolving. METHODS Census microdata from 39 countries and 19,000 local units have been pooled 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 of the countries, the spatial autocorrelation statistics indicate that there is substantial spatial heterogeneity. CONCLUSIONS Our results lead us to ask what forces may have shaped these patterns, and they remind us that these forces need to be taken into account when seeking to explain recent cohabitation patterns, and especially the rise in cohabitation.