The contemporary emphasis on the pathologies of shelter denizens and street dwellers tends to conceal the great variety of makeshift ways of life that have characterized "homelessness" over the centuries. Diversity notwithstanding, those considered "vagrants" were historically marked as suspect members of a poor apart, even when their numbers increased sharply. Because kin ties have consistently proven to be the first line of defense against "literal homelessness," skid row researchers thought their absence (along with the lack of associated ties to work and community) to be diagnostic of the condition. Indeed, earlier research tended to see as "homeless" any "disaffiliated" persons, housed or not, who lived alone in unconventional dwellings. Not only have the new homeless poor, by contrast, proven to be more diverse -- their geographic locus, age, gender, ethnicity, and signal disabilities having all changed -- but their common element is less often ascribed to faulty social connectedness than to sheer absence of shelter. This paper discusses such changes and reviews definitions of homelessness and several approaches to its social construction. The paper argues that, although definitions owe as much to political as to logical considerations, it makes both practical and historical sense to view the streets and shelters as but one variant of a class of informal or makeshift residential settings that increasingly characterizes the marginally situated.