CITIESwere not confined to distinct neighborhoods
(Sjoberg 1960).
Beginning in the tenth century, further town
development in the West was facilitated by increas-
es in agricultural technology, population, trade,
and communication; the rise of an entrepreneurial
class; and an expanding web of social norms re-
garding economic activity. Communication and
manufacturing were revived, which led to the
growth of towns with local autonomy and public
administration, and eventually to networks of cit-
ies. Surplus rural populations migrated to towns
and cities, which grew because of their specializa-
tion and larger markets, becoming focal points of
European societies (Hawley 1981, pp. 37–83).
The emergence of a global economy struc-
tured city development (Lo and Yeung 1996, pp.
1–13). In the thirteenth and fourteenth centuries,
some European central place and port cities, such
as those of the Hanseatic League of Northern
Europe, established commercial links with others.
Meanwhile, other cities in the Eastern Hemisphere
and some cities in the Western Hemisphere were
linked together by long-distance trade routes tran-
scending the boundaries of empires and states
(Wolfe 1982, p. 250). Military-commercial alliances
facilitated the incorporation of territories into
states. Commercial ties expanded during the late-
fifteenth and the sixteenth centuries, as Europe-
ans developed merchant capitalism, and traded
with and colonized peoples on other continents.
European and North American states developed
more complex economies during the next three
centuries, facilitating development of a ‘‘Europe-
an world economy’’ with a global market, a global
division of labor, and a global system of cities
(Wallerstein 1974).
WESTERN CITIES SINCE THE INDUSTRIAL
REVOLUTIONIn most regions of the more developed world,
urban growth and urbanization have occurred at
an increasing rate since the beginning of the In-
dustrial Revolution. After 1820, the numbers and
sizes of urban areas and cities in the United States
increased as a result of employment concentration
in construction and manufacturing, so urban are-
as began to grow more rapidly than rural ones.
The population classified as urban by the U.S.
Census Bureau (based on aggregations of 2,500 or
more and including the surrounding densely popu-
lated territories) increased from 5 percent in 1790
to 75 percent in 1990. In 1790 the largest urban
place in the United States had fewer than 50,000
inhabitants. As late as 1840, not a single urban
place in the United States had more than half a
million inhabitants. There were four such places in
1890, fourteen in 1940, twenty-two in 1980, and
twenty-three in 1990 (U.S. Bureau of the Census
1997, p. 44).City growth in the United States during the
nineteenth century was driven by migration, since
there were sometimes excesses of urban deaths
over births in the early part of that century and
lower birthrates in the last part of that century.
Population concentration facilitated greater divi-
sions of labor within and among families and
individuals, as well as increasing numbers of vol-
untary associations centered on new urban inter-
ests and problems. At first, cities were compact,
growth was vertical, and workers resided near
their workplaces. The outward expansion of the
residential population was facilitated in the last
part of the century by steam and electric railways,
the outward expansion of industry, and the in-
creasing role of the central business district in
integrating economic activities (Hawley 1981,
pp. 61–145).The increasing scale of production in the Unit-
ed States led to the development of a system of
cities that organized activities in their hinterlands.
Cities were differentiated from each other by their
degree of dominance over or subordination to
other cities, some of which were engaged in cen-
tralized manufacturing, others of which depended
on transportation, commercial, administrative, or
other functions. According to Hawley (1986), cit-
ies may have certain key functions that dominate
other cities, that is, integrating, controlling, or
coordinating activities with these cities. Examples
of key functions are administration, commerce,
finance, transportation, and communication (Dun-
can et al. 1960). Since each city exists within its
own organizational environment, the expansion
of linkages of urban organizations has accompa-
nied the development of a system of cities (Turk 1977).In the United States, the nature of key func-
tions in city systems changed with the expansion of