The terms historically used to describe them include "bums," "hoboes," "migrants," "street people," "transients," "tramps," and "vagrants." Just as varied as the words we have used to describe them are the reasons many people have found themselves living in the land of opportunity without permanent residence.

The book considers homelessness and its distinctive character in three periods of American history: the era of tramps and hoboes in the late 1800s-early 1900s, the era of transients and migrants in the 1930s, and the era of homeless and "street" people in the last 40 years. It...