In North America almost everyone has assumed that, from the 1860s to the 1960s, suburbs were healthier than cities, but this has not been established as fact by urban or demographic historians. Contemporary evidence is scattered but, especially for the interwar years, significant. The most useful data pertain to infant mortality rates. They indicate that, in terms of population health, suburbs were diverse and so were city neighborhoods. On the average, suburbs were healthier than cities but, partly because of poor sanitation, many unincorporated fringe areas were as unhealthy as the worst city slums. As mortality rates declined, so did the relative advantage of suburbs; in the early postwar period the widespread use of septic tanks caused problems. Future research should utilize neglected, published data and, where possible, supplement these with the analysis of vital records.