In Mexico-City, like in most metropolitan cities, intra-urban residential mobility is the main driving force behind the settlement pattern and reworking of the social division of space. In the colonias populares, illegal settlements which remain an inescapable feature of urban growth, the dull grey aspect of the block-built houses dominates the landscape and poverty is prevalent. However, these characteristics are insufficient to properly grasp these areas, where complex processes of inhabitant s’anchoring are at work. This paper aims to understand the mechanisms of residential anchorageand the relationship between the various forms of anchorage and the socio-spatial changes and developments. Reading the trajectories of the particular places through the prism of the inhabitants’ trajectories gives clues for understandinga certain maturation of the peripheral colonias populares. The analysis of residential mobility, through systematic sources (censuses, detailed samples) and exploratory surveys, can shed light on links between places and the variety of experiences of their inhabitants and contexts. These results, on the one hand, render insufficient the sole approach of studying socio-spatial relegation systematically followed by urban consolidation on and, on the other hand, reveal a socio-spatial stratification that would be poorly represented using the notion of fragmentation.