The Death and Life of Great American Cities

This chapter focuses on the first condition that generates city diversity: primary mixed uses. Jacobs emphasizes the economic effects of this condition. Simply put, diverse businesses need diverse users to survive and thrive.

Consumer enterprises rely on foot traffic occurring at different times of day, without which they can disappear (or never appear at all). According to Jacobs, this continuity of movement on sidewalks “depends on an economic foundation of basic mixed uses” (153). Many enterprises are unable to survive on residential patronage alone. Their existence depends on residents, but also on outside workers and visitors to the area. The presence of people attracts more people, thereby encouraging more diversity.

Jacobs stresses the importance of time spread. Some areas lack diverse industries because they are only densely populated during certain times of day. Downtown areas, for instance, are generally busy midday when office workers go to lunch, but empty at other times. Strategic infusion offers a path forward. For example, adding tourist attractions, such as concert halls or landmarks, increases the number of bodies in a downtown area at different times of day. The creation of new attractions is essential to this approach, but Jacobs cautions against the wholesale replacement of existing structures. New uses should also accord with the character of the district.

Jacobs discusses two kinds of diversity: primary and secondary. Primary uses bring people to specific places. Offices, factories, dwellings, and places of entertainment and education are all primary uses. The combination of two or more primary uses putting people on streets at different times is economically stimulating. Secondary diversity refers to enterprises that grow in response to primary uses. In other words, secondary diversity serves the people drawn to areas by primary uses. Expanded street use, spread throughout the day, can support diverse enterprises. The more mixed the pools of users, the more services and shops will develop.

Three factors determine the effectiveness of primary mixtures. First, users must use the same streets at different times of day. Second, these users must use some of the same facilities. Third, these users must have “some reasonable proportionate relationship to people there at other times of day” (164). In other words, pools of users must overlap in varied and complex ways.

Jacobs emphasizes downtown primary mixture, not because it is unnecessary elsewhere, but because the lack of primary uses is “typically the principal fault in our downtowns, and often the only disastrous basic fault” (164). Downtown areas also have a direct impact on other parts of cities. An economically strong downtown, for example, can have a ripple effect on other districts.

Decentralization creates a vacuum. In a healthy city, however, less intensive uses are constantly being replaced with more intensive ones. Market forces can push some enterprises out of central areas and into outlying districts. Secondary diversity that is crowded out must relocate to an area where secondary diversity can thrive; namely, in places with mixtures of primary uses. Their movement generates more diversity and helps create a more complex city. When primary diversity gets crowded out, it can relocate to an area where primary use is lacking. The move helps form new pools of primary mixed uses. All primary uses move differently, but they “must be employed in concert to accomplish much” (167). Although public policy cannot directly move private enterprises into particular locations, it can encourage their growth indirectly using primers, or primary-use chessmen. Carnegie Hall in New York City, which led to the opening of restaurants and other enterprises in its vicinity, exemplifies this process.

According to Jacobs, planning problems “arise chiefly from theories which are in arbitrary contradiction with both the order of cities and the needs of individual uses” (172). The unsuitable theories she is most critical of relate to the City Beautiful and Garden City movements. Rather than creating monumental areas separated from the surrounding urban fabric, which “contradicts the functional and economic needs of cities” (173), Jacobs promotes a vision of a “mingled city with individual architectural focal points intimately surrounded by the everyday matrix” (174), which is “in harmony with the economic and other functional behavior of cities” (174). This vision echoes the aesthetic theory of Pierre L’Enfant.

Predominantly residential areas also benefit from complex and varied primary uses. Jacobs dismisses the orthodox idea of separating dwellings from work. In contrast to downtown areas, however, the lack of primary mixture is only one hurdle facing residential areas, and sometimes not the most urgent. In residential areas, it is common to find deficiencies in most, if not all four, conditions for generating diversity. One must look to existing enterprises in these areas to build “from existing assets, to make more assets” (176). It is sensible to begin where a condition for diversity already exists.

Gray areas of cities are the most problematic, first because they lack commercial foundations to build upon, and second because of the absence of high-density dwellings. Jacobs observes that these areas don’t have a chance unless other gray areas are diverse and nurtured and downtowns are reinvigorated for all hours of the day (177). The ability of a city to generate diversity and vitality in any of its parts can lead to success in its most problematic districts. 

This chapter focuses on the second condition that generates city diversity: short blocks. Jacobs details the shortcomings of long blocks, whose physical isolation from the surrounding fabric negatively impacts the social and economic fiber of neighborhoods. People on long streets, for instance, can form pools of economic use only at intersections, where their streets come together in a single stream. These intersections are problematic because they become places where enterprises cluster, leading to “a depressing predominance of commercial standardization” (180). Long, monotonous, dark streets interrupted by commercial clusters are salient features of urban failure.

Unlike isolated long blocks, short blocks “mix and mingle” (180) with each other, doing away with the monotony of long blocks. They encourage commercial enterprises at economically viable spots, increasing the distribution and convenience of such businesses. Additionally, they allow people to vary their routes by taking different streets, creating more fluidity.

Long blocks sort people into different paths that only meet infrequently. They create a physical barrier between different uses, even when they are located in close proximity. Long blocks hinder incubation and experimentation, as well as small enterprises that depend on drawing customers from a large cross-section of passersby.

Streets in successful neighborhoods tend to multiply, yet orthodox planners view them as wasteful. Garden City and Radiant City theorists objected to the use of land for streets because they wanted to use that land for open spaces. The designers of housing projects also fail to understand the benefits of short streets. They create long blocks, or malls, sometimes with streets at regular intervals, but these streets are meaningless because most people rarely have use for them. The streets on these mega-developments are also meaningless visually, having similar scenes. Short, frequent streets, on the other hand, create an intricate fabric of cross-use, thereby “generating diversity and catalyzing the plans of many people besides planners” (186).

This chapter focuses on the third condition that generates city diversity: aged buildings. Jacobs argues that old buildings are necessary for vigorous streets and districts to grow. Her definition of aged buildings includes “museum-piece old buildings” that are in excellent condition, in addition to rundown structures. These old buildings, however, must coexist with new construction to create a diverse neighborhood.

Neighborhoods composed exclusively of new buildings can only support enterprises that can afford the high cost of new construction. Enterprises pay for the high overhead out of their profits, or with lucrative subsidies. Well-established businesses with a high turnover, such as chain restaurants and supermarkets, can afford new construction, as can well-subsidized enterprises like museums. However, the high cost of new construction excludes modest businesses, including neighborhood bars and pawn shops, as well as informal feeders of the arts, such as galleries and studios. These modest enterprises generally open in older buildings, where the rent is less expensive.

Diversity in building age is critical to a neighborhood’s economic health. Wealthy businesses that can afford new buildings also need old construction. Without a blend of old and new buildings, and the varied enterprises each attracts, wealthy businesses are “part of a total attraction and total environment” (188) that is too limited economically, and therefore too limited functionally, to be an interesting, lively, and convenient neighborhood. For diversity to flourish, high, middling, low, and no-yield enterprises must intermingle. Ideally, new buildings in mixed neighborhoods will replace old ones over time, and old buildings will be rehabilitated gradually. This type of development allows structures of different ages and types to coexist in a single area, supporting mixed primary uses over the longue durée.

Large housing projects erected at one time are homogeneous and do not easily accommodate diversity, commercial or otherwise. These projects have poor staying power and lose their appeal over time. Moreover, they are often protected from new commercial competition. This type of monopoly planning financially bolsters enterprises that may not otherwise thrive or survive, but it cannot create city diversity. When large projects built at one time are new, they offer no economic possibilities for diversity. By the time they age, low value is their only useful attribute. Housing projects do not change physically over time, beyond the gradual decay of their physical fabric, but attitudes toward them change. Over time, people view them as stagnant and undesirable. Eventually, they are demolished, and the cycle begins anew. Jacobs objects to the perpetuation of this cycle, advocating instead for extra streets, high density, room for primary and secondary uses, and the strategic preservation of the old.  

This chapter focuses on the fourth condition that generates city diversity: the dense concentration of people. High-density areas support varied specializations, resulting in convenience. Scholars have studied the relationship between high density and convenience as it relates to downtowns, noting that without high density, diversity would not exist. However, they have given little attention to this relationship as it relates to primarily residential areas, an imbalance Jacobs seeks to address.

Dwellings form a large part of most cities. Residents are the main users of the streets, parks, and businesses surrounding their homes. Dwellings must be supplemented with other primary uses to draw people outside at different times. Without a high concentration of residents, however, convenience and diversity are impossible.

Orthodox planners typically blame high dwelling densities for many urban ills, but in many cities, no such correlation exists. In fact, many overcrowded slums in the United States have low dwelling densities. That is not to say that all high-density areas do well. The relationship between high density and diversity is complex, and the former on its own does not necessarily result in the latter. The high concentration of people is simply one necessary condition for diversity.

High density dwellings have a bad reputation because they are often confused with overcrowding, but the two are not synonymous. High density refers to “large numbers of dwellings per acre of land” (205), whereas overcrowding refers to “too many people in a dwelling for the number of rooms it contains” (205). The blurring of the two stems largely from the Garden City Movement. Overcrowding is generally a symptom of poverty and discrimination. It is more destructive in low densities areas, such as gray belts. Excessive density in these zones results in a different kind of settlement, one that brings city problems, but without the benefits of city life. Jacobs refers to this as in-between densities. Under the right circumstance, high density dwellings can foster diversity, while overcrowding works at cross-purposes to diversity. There is no single correct dwelling density. Performance determines if the balance is right. City dwelling densities, therefore, should go as high as necessary to stimulate diversity. The rule of thumb of orthodox planners, 20 dwellings or fewer per acre, is not applicable to cities.

Jacobs favors variation in dwelling design in high density cities over standardization and full efficiency. The greater the range and number of dwellings, the better. Lack of formal variation in domestic architecture leads to decline in diversity of population and enterprise. Jacobs cites Greenwich Village as an area of high density with formal variety in its domestic architecture. Density and variety coexist in this neighborhood because “a high proportion of the land which is devoted to residence (called net residential acres) is covered with buildings” (214). By contrast, housing projects that leave land open for playgrounds use their land inefficiently. Local zoning and federal fiat impose rules that make variety in public housing virtually impossible. Constructing new buildings in separate locations presents a solution to the problem of low densities. New construction increases variation if builders add the structures gradually.

High-density areas require frequent, interlaced streets to generate diversity. These streets constitute open land, which can have a thinning impact on population density. A successful neighborhood combines numerous streets, vibrant parks in well-trafficked places, and non-residential uses with high-density dwellings.

This chapter debunks the negative myths associated with diversity, the perpetuation of which has shaped city zoning regulations. According to Jacobs, these myths “rationalized city building into the sterile, regimented, empty thing it is” (222), actively hindering improvements to city planning.

Myth 1: City diversity is chaotic and innately ugly. This myth implicitly values standardized, homogenous design over variation. A diverse city is not chaotic. Rather, it is ordered complexly through intricate mixtures of buildings and uses. Sameness is visually monotonous. Jacobs blames zoning laws for this monotony because “they permit entire areas to be devoted to a single use” (229). Though sameness in design appears ordered, it lacks directionality, making it aesthetically disordered. Sameness also leads to the creation of superficial differences that are meaningless and chaotic. By contrast, diversity of uses offers the possibility of real differences that can produce visually stimulating effects. According to Jacobs, the problem of accommodating diversity visually, while also maintaining a sense of order, is the “central aesthetic problem of cities” (229). 

Myth 2: City diversity causes traffic congestion. Vehicles cause congestion, not people or diversity of uses. Congestion occurs in thinly settled areas that require cars, or where diverse uses are infrequent, such as shopping centers and movie theaters. These uses concentrate traffic by localizing it in a particular place at a particular time. The lack of concentrated diversity puts people in their cars for most of their needs. Roads and parking lots cause more sprawl, which leads to an even greater reliance on automobiles. Dense, diverse cities make room for, and encourage, foot traffic.

Myth 3: City diversity invites ruinous uses. This myth assumes that permissiveness of use leads to destruction. Jacobs counters this myth with different examples of diverse uses, some of which are actually harmful, others of which are conventionally understood to be harmful. Junk yards fall in the former category. They do not contribute to the convenience or attraction of an area, nor do they help concentrate people, yet they occupy large swatches of land and are visually repellent. Simply put, junk yards are blight. Successful city districts are never dotted with junk yards. Space-hogging, low economic uses like junk yards crop up in areas that are already unsuccessful. Diversity of uses is not the problem. Getting rid of junk yards requires cultivating a fertile economic environment that makes more vital land uses both logical and profitable.