Encircling walls had been a feature of urbanization for millennia and, until the modern era, fortified walls protected cities in Europe and Asia from predation by other urban civilizations as well as from the devastating raids of nomads. In contrast, the small, rapidly growing cities of colonial America made due at first with wooden stockades and later with flexible defensive infrastructures; the sheer distance of threatening forces meant that militias, and afterward a standing army, police force, and network of forts and prisons, sufficed as protection.
To this day, the paucity of walls along American streets attests to the nation’s long history of urbanization without walls — and helps explain why gated communities often seem so startling. It was in fact the absence of walls that set American cities apart from most old world development.