The predictive power of three intersecting environmental dimensions on late-life walking was investigated: built structures, social infrastructure, and social capital, conceptually based on the ecological framework of place within a life course perspective, which posits that a living environment is simultaneously a physical place, a social place, and a set of social bonds. Multilevel models were used to examine the extent to which environments defined as interactions of the social and material environmental dimensions reliably predict walking for transportation among U.S. adults aged 60 or older in the 2015 National Health Interview Survey (n=11,180). Random intercepts representing 221 environments showed an intraclass correlation of 21%, indicating high levels of between-environment variance in walking. Social infrastructure had the highest predictive power for walking, followed by material structures and social capital. Synergistic interventions that incorporate the intersecting nature of the socio-material environment may be most effective in promoting physical activity in later life.