There is hardly any city in North America that does not have a central area with a grid pattern. Many South American cities share this feature and a good number of European ones as well. This universal use of the grid as a stencil to plan new cities is intriguing.
Where did this stencil come form?
It is often called the Hippodamian grid after the Greek town planner who used it to lay out his home town after its destruction by invaders. Yet we do know that he was not its inventor. Many early cities appear on archeological lists that precede Hippodamus and his most celebrated layout of Miletus.
If he borrowed the idea from other cities that he happen to visit, why did he think it was a good solution? After all the majority of ancient cities grew by accretion, organically, and did not show any signs of pure geometry, including the most celebrated city during his lifetime –Athens – in which he had admirers and critics.
That he was, allegedly, a Pythagorean disciple may explain his proclivity toward geometric forms but does not explain his decision to borrow and apply this stencil.
The first evidence of grid-like layouts for settlements in Mesopotamia and the Hindus valley goes back to around 2500, that’s about two millennia before Hippodamus’ time and as far back removed as we are from his invention/adoption.
What then brought the first grid-like layouts into existence? Most likely the same forces that shaped the highway network of this century – a new means of transport.
According to a chronology of events listed in a recent book, the agrarian period in history that brought about permanent human settlements started at about 4000 BCE and along with it came animal transport. Five hundred years later, around 3500 BCE, wheeled transport emerges. One thousand years after it surfaced the first grid-like settlement layouts appear.
Like the car, early wheeled transport must have had a difficult time adjusting to the organic, maze-like layout in which it was introduced. Carts and chariots cannot negotiate sharp turns and move best on a straight line. Frequent t-intersections or turns make the tip long and arduous. In addition, carts and particularly chariots are normally drawn by two horses. Two attributes of the old street layouts would have made access to places either impossible or very difficult: the width of streets and the maze-like pattern. A third would also seriously hinder access –slope. Many settlements that were built on hill sloes and tops, for defense purposes would be unable to accommodate the new technology. Naturally, when the friction between existing street patterns and new transport means became intolerable a new street pattern emerged. It would not be hard to see why Hippodamus would have readily adopted it.
To see striking examples of streets that are inaccessible to carts and chariots look up Fez the Old city in Flikr or my postings of Greek island streets also in Flikr
The book that lists the chronology of transport revolutions is: “Maps of time: An Introduction to Big History” by Cristian, D. (2004)