Small Blocks

Definition

Small blocks are the second of Jane Jacobs's four conditions for city diversity: "Most blocks must be short; that is, streets and opportunities to turn corners must be frequent" (Jacobs 1961, p. 150). The mechanism is path-mixing: long blocks "automatically sort people into paths that meet too infrequently, so that different uses very near each other geographically are, in practical effect, literally blocked off from one another" (p. 180). Her exhibit is Manhattan's West 88th Street, whose 800-foot east–west blocks pool all their users into one stream on Columbus Avenue, producing "endless stores and a depressing predominance of commercial standardization" around "the dismally long strips of monotony and darkness — the Great Blight of Dullness, with an abrupt garish gash at long intervals" (p. 179). The positive exhibit is an added street — not a "sterile 'promenade'" — where "things could start up and grow at spots economically viable": with an extra street, "the neighborhood would literally have opened up to him" (p. 179).

The concept carries a planning-theory reversal: the myth "that plentiful city streets are 'wasteful'… comes of course from the Garden City and Radiant City theorists who decried the use of land for streets because they wanted that land consolidated instead into project prairies" (p. 185). Against it Jacobs assembles the evidence — Greenwich Village's diversity extending east through "unerringly the direction of short blocks and fluid street use" while Chelsea languishes "behind its barriers of long, self-isolating blocks" (p. 183); the East Side's five intersecting avenues against the West Side's two (p. 184n); Philadelphia's 400-foot blocks halved by alleys-become-streets in exactly the districts where commerce lives (p. 185).

Key Thinkers

• Jane Jacobs — the concept's author: fluidity of use, not homogeneity of architecture, "ties together city neighborhoods into pools of city use" (1961, p. 181).
• Gordon Cullen & Ian Nairn (not yet paged — see log) — the Outrage/Counter Attack pair Jacobs cites for visual interruption and street unification (p. 390n).

Related Concepts

• mixed-primary-uses — short blocks are the means; mixture is the end: "Frequent streets are not an end in themselves" (p. 186).
• attrition-of-automobiles — short blocks "interfere with traffic flow" (p. 364): the diversity tool doubles as traffic-calming.
• separation-of-uses — the block-size corollary of the sorting doctrine: super-blocks as "project prairies."
• organized-complexity — the analytical frame: the street network as an interrelated, not additive, system.

Source Support

Sources in the wiki that discuss this concept:

• The Death and Life of Great American Cities (Jacobs 1961) — condition 2 stated (p. 150; Ch. 9, pp. 178–186); the West 88th Street thought-experiment (pp. 178–180); Rockefeller Plaza as added street (pp. 181–182); the Chelsea/Village divergence and the elevated-railway "mystery" (pp. 183–184); the "wasteful streets" myth traced to Garden City theory (p. 185); super-block malls as "streets… meaningless because there is seldom any active reason for a good cross-section of people to use them" (p. 186); the eight to ten spontaneously enlivening long blocks of Manhattan (p. 182); visual irregularity as a bonus of added streets (Ch. 19, pp. 379–381).

Source Support linking rule: All entries in this section must be wikilinks to source note pages in wiki/source-notes/ using the source-notes/ path prefix. Never link to raw files — raw files are not wiki pages.

This page requires fuller treatment — created at the Jacobs ingest; awaits the space-syntax literature (Hillier & Hanson on permeability, gamma-analysis) that formalized the block-length claim.

Open Questions

• Jacobs herself notes short blocks are "a means toward an end": if diversity is generated by repressive zoning elsewhere, "nothing significant can be accomplished by short blocks" (p. 186). How does the condition interact with the wiki's missing-middle-housing and new-urbanism pages, which prescribe connected grids inside a development — Jacobs's mechanism or its simulation?
• The East Side–West Side comparison rests on mid-century Manhattan. Do block-length effects hold under app-mediated commerce and delivery logistics, or is the corner's economic function now substitutable?