The Twin Cities Phenomenon

I would like to point out how it can be seen the way the U.S. was settled simply by looking at a map. America has three prominent sets of twin cities; Minneapolis-St. Paul, Dallas-Fort Worth and, San Fransisco-Oakland. I will define a twin city as two major metropolitan areas that are geographically distinct yet close enough to share an airport. A growing city absorbs sorrounding communities but twin cities are similar enough in scope that neither can absorb the other.

A city is usually defined as the focal point of a hinterland encompassing the non-farming operations of an agricultural watershed. Using this definition, a twin city seems to make no sense. If a city is the focal point of an agricultural hinterland, then why would there be a twin city?

The answer depends on the context in which the land is settled. A city begins because there is something desirable about the location, such as resources or central location. If the settlement of the land was planned, there should be no such thing as twin cities.

But if it was settled by free-ranging pioneers, then two groups could decide independently to settle in a desirable area and grow into twin cities. This is why America's three sets of genuine twin cities are all in the western part of the country. Cities in the east were started by colonists more-or-less under orders from a government while cities in the west were mostly started as settlements by small groups of pioneers.