The Death and Life of Great American Cities

Jacobs attacked the urban planning orthodoxy of the 1950s, which favoured separated land uses, superblocks, tower housing in open space and the clearance of neighbourhoods deemed slums. She argued from direct observation that this approach destroyed the conditions that make cities work, and she wrote as a journalist and resident rather than as a planner.

Her central argument is that cities depend on dense, mixed, continuous street activity. She identifies four conditions for diversity: a district must serve more than one primary function so that people are present at different times of day; blocks must be short so that routes intersect and streets are used; buildings must vary in age and condition so that rents vary and different uses are affordable; and density of population must be sufficiently high.

The eyes on the street concept holds that public safety comes from continuous informal observation by people who have reason to be present, not from policing or from design that separates people from streets. She develops the idea of the sidewalk as the site of unplanned contact that builds the trust a neighbourhood runs on. Her attack on urban renewal is specific and she documents projects that destroyed functioning neighbourhoods and produced the conditions they were meant to remove.

Jacobs opposed Robert Moses directly and stopped the Lower Manhattan Expressway. Her framework has been criticised for underweighting the role of housing supply and for having been adopted by residents opposing development, which uses her arguments against the density she advocated. Her observational method has no statistical apparatus, which specialists note. The four conditions remain the standard framework for thinking about urban vitality.