Internal Structure: Three Classic Models, and Cities Beyond North America

The three classic models

Concentric zone (Burgess, Chicago 1925). Rings around the CBD: a transition zone of factories and deteriorating housing, then working-class housing, then better residences, then a commuter zone. The engine is invasion and succession: as immigrants arrive, groups move outward ring by ring. Strength: it captures the pedestrian and streetcar city, where distance to the centre governed everything. Weakness: it assumes one CBD and flat, uniform land, and it cannot accommodate the automobile, edge cities, or physical barriers.

Sector (Hoyt, 1939). Land uses grow outward in wedges along transport corridors. Once a high-rent sector is established, it extends outward along the same axis; industry follows rail and river lines. Strength: it explains why wealth is often a corridor rather than a ring, and it builds in transport. Weakness: still radial from one core, and it says little about nodes off the axis.

Multiple nuclei (Harris and Ullman, 1945). A city grows around several specialised nodes — a university, an airport, a port, an office park — because some uses need each other and some repel each other (heavy industry and high-status housing), and because some can pay high rents while others cannot. Strength: it fits the automobile metropolis and edge cities. Weakness: it has little predictive structure — it describes rather than forecasts.

The later galactic (peripheral) model extends this: an old core surrounded by edge cities strung along a beltway.

Models outside North America

Latin American (Griffin-Ford). A colonial CBD with a commercial spine running out to an elite residential sector; then a zone of maturity of consolidated housing; a zone of in situ accretion still improving; and an outer zone of peripheral squatter settlements. Disamenity zones — areas so poor and unserviced that authorities barely enter — cut through the city.

Sub-Saharan African (de Blij). Often three CBDs: a colonial CBD of vertical buildings, a traditional CBD of single-storey shops, and an open-air market zone; ethnic neighbourhoods; and informal settlements at the edge.

Southeast Asian (McGee). No single formal CBD. The focus is the old colonial port zone, with an alien commercial zone (often Chinese-run) beside it, a mixed land-use zone, and market gardening on the fringe.

The common thread outside North America: the poorest housing is on the periphery, not the inner ring — the reverse of the Burgess pattern.