Although the commissioners considered the grid advantageous for housing, by the mid-19th century, urban critics were more aware of its disadvantages: the densely built grid deprived residents of open space, sunlight, and air. These deprivations were fundamentally due to high land values and lot coverage, not the grid per se, but it is easy to see why slum conditions, largely played out in 20-by-100-foot lots, were attributed to the grid.
Efforts to improve tenement building standards failed to improve what was already built, and in the 20th century, reformers turned to a new strategy: building demolition, site clearance, block aggregation, and new housing solutions on superblocks. This redemptive view of superblocks converged with the ascent of modern urban theory, which disregarded streets and favored free-standing towers in open space. The superblock carried a 20th-century social reform agenda.
The tower-in-the-park model guided the development of both middle-income and public housing in New York beginning in the 1930s. Exerting the powers of eminent domain, the city took possession of large areas, cleared the tenements, closed the streets, merged several blocks into one, and scattered the superblock with apartment buildings. The buildings were often oriented to the sun, not the grid. The demapped streets contributed to the open space of the site, while the bounding streets were sometimes enlarged to handle the displaced traffic.
The area along the East River was dramatically altered by superblocking from 42nd Street to the Williamsburg Bridge. This aerial view from 1952 shows, from north to south, the United Nations building under construction; two middle-class housing projects, Peter Cooper Village and Stuyvesant Town; and three public housing projects: Jacob Riis, Lillian Wald, and the Baruch Houses, for which clearance had just begun on the area directly north of the Williamsburg Bridge.