Source: Adapted from M. Domosh, R.P. Neumann, P.L. Price and T.G. Jordan-Bychkov (2009) The Human Mosaic: A Cultural Approach to Human Geography, 11th Edition, Cranbury NJ: W.H. Freeman.
Historically, two factors impacted the location of cities: their defense and commercial capabilities. Defensive capabilities are more of a site issue since they rely on a defensible physical location that does not necessarily provide good access. At the same time, commerce is more a situation issue that expands the opportunities of a site by placing it within a broader framework of commercial relations.
- Defense. An array of sites offers various defensive advantages that can be enhanced by building fortifications. This mainly refers to cities established before the Industrial Revolution, since defense was a prime consideration. River meanders and islands are good examples of defensible sites, with cities such as New Orleans and Paris as prime examples. For cities involved in maritime trade, the coastline also offers defensible sites, such as a peninsula (or an offshore island), as in Boston and Hong Kong, or a sheltered harbor site, as in New York and Rio de Janeiro. The presence of a promontory can further expand the defensive capabilities of any of the above sites. Modern forms of warfare, particularly artillery, rendered many defensive attributes, such as fortifications, irrelevant.
- Commerce. With the Industrial Revolution, and in several cases, well before, trade relations became important location factors, with accessible sites along river systems particularly suitable. Bridge-point sites are locations where a bridge could be constructed more easily, such as a narrower and shallower river segment. For instance, London was the first suitable site along the Thames River where a bridge could be built. A confluence site benefits from the accessibility of two (or more) river systems, as in the cases of Pittsburgh and Chongqing. Portage sites are established to link two river systems that would otherwise be unconnected, such as Chicago (the Great Lakes and the Mississippi system). High land transportation costs prior to the Industrial Revolution underscored the importance of head of navigation sites, which were the furthest convenient locations that could be reached. Montreal and Minneapolis are such examples.
Improvements in engineering capabilities in the later stages of the Industrial Revolution would make the advantage of rivers for commercial sites less relevant, particularly with the development of rail and highway systems. Still, once a location has been selected and capitalized upon, the city will remain even if the initial location factors are no longer highly relevant. Thus, a large share of the world’s urban agglomerations was set using some of the above location factors. Of all these considerations, good maritime access remained an important consideration due to the commercial significance of maritime shipping.