Situations for defence originally most important. - Later trade routes located by topography create commercial cities, where break in transportation occurs. - In manufacturing, extractive Industries follow raw materials, and cheap power, and later seek the largest cities for labor supply, home markets and cheap transportation. - Political locations compromises. - Exact starting points analyzed. - Topographical influences most compelling.
Situations favorable for defence determined the location of ancient cities, as with the Greek colonies on a promontory or an island, the Etruscan cities on hill tops, Athens with the Acropolis, Rome on seven hills, Paris on an island and London in the midst of swamps. In modern times the individual settler locates his cottage to satisfy his first needs for water, wood, grass, shelter, etc., and small settlements are widely scattered in all available spots. It is largely geographical superiority which renders certain localities capable of satisfying more extensive demands and lifts small settlements into cities.
Trade routes, the lines of least resistance between the sources of products and their final markets, have in all ages located commercial cities at the points where a break in transportation occurs. Where a trade route traverses an ocean or lake, cities arise at the harbors which have easy topographical approach from productive regions and from which markets can be readily reached. For example, the phenomenal growth of New York is due to there being but one topograhically easy route from the West through the Appalachian Range to the Atlantic Coast, concentrating the flow of products to New York, aided first by the Erie Canal and later by the New York Central and other railroads. Where a gulf exists, the trading city is commonly located at the innermost angle, as with Christiania, Liverpool, Genoa, Naples, Venice and Hamburg. Where the action of the sea closes harbors, ancient cities were ruined, as with Ephesus, Utica, and the coast cities of Asia Minor and northern Africa, while modern cities retain their harbors by constant dredging.
Where the trade route follows a river, cities arise either near the mouth where ocean and river navigation meet, as at New Orleans or Philadelphia, at the head of rivers where river and creek navigation meet, as at Albany, Richmond and St. Paul, at the confluence of two or more rivers or branches of the same river, as at St. Louis, Omaha, Mayence, Coblentz, and Cairo, at the intersection of a river and a canal, as at Richmond, Syracuse, Evansville, and Fort Wayne, at an obstruction in the river requiring unloading, as formerly at Louisville, or at a marked bend changing the direction of a river, as at Cincinnati, Kansas City, Madgeburg, Toulouse, and Lyons. A river in forming a natural highway forms also a natural barrier to intercourse between its two sides, so that facilities for crossing the river may so concentrate travel as to create a small trade route and thus a town at the river crossing. For example, Harrisburg started at a ferry across the Susquehanna River; Rockford and Reading at fords in the Rock and Schuylkill Rivers, and Terre Haute at the bridge of the National Pike, across the Wabash River. Deep water in rivers will locate cities, as with Memphis, Vicksburg, Natchez, Bremen, Rotterdam, Antwerp, and Havre. New Orleans owes its location to the fact that the land on which it was built was a few feet higher than any river land within many miles of it.
Constantine, North Africa. Typical site of ancient Mediterranean city on flat-topped hill, chosen for defence.
Land trade routes, prior to the time of railroads, created cities at their intersections, commonly in the centre of great plains, as with Paris, Vienna, Moscow, Berlin, and Prague. Other points were where plain and mountain met, requiring a change in transportation, as with Turin, Milan, Augsburg, and Munich. The old trails from the Missouri River to the West caused the beginning of a number of towns as oufitting points, such as Council Bluffs, St Joseph, and Topeka.