# Chapter 1: The Permanent Framework What are cities made of? We tend to think of what we see: cars, people, buildings, shops, street signs, sidewalk cafes. These are the things we notice, that seem to define urban life. But beneath this churning surface lies something older and more permanent. Cities are not just their buildings, though we often think of them that way. Nor are cities just their people. Rome had a population of a million in the first century of the Common Era, but after the empire collapsed, that number plummeted to 60,000. The population didn't reach a million again until the 1930s. The buildings changed, the people changed, the entire civilization changed. Yet it was still Rome. So what persisted? What is the actual substance of a city that allows it to maintain its function across millennia? To understand cities, we need to think like archaeologists, peeling back layers of time. At the surface, we find the most fleeting elements: paint colors, swing sets, stop signs, yard art. These things last months, years, maybe decades. Dig deeper and we find people. Individually, we last about 80 years. Collectively, our migration patterns can ebb and flow on similar timescales. Below that, buildings. A big-box store might last 15 years before it's torn down or vacated to ruin. A well-maintained house might make it 150 years. The average building splits the difference at about 80 years, interestingly about the same as a human lifetime.[^1] Notice something important: all these elements (the ephemeral decorations, the people, the buildings) exist primarily in the realm of private property. They're owned by individuals or corporations, maintained by them, and when those owners move on or die, the maintenance often stops. It's hard for any individual to make something last beyond their own lifetime. But as we dig deeper into the city's archaeological layers, we begin to find elements that are publicly owned: bridges that span centuries, parks that have hosted generations of picnickers, monuments that have outlasted the regimes that built them. We collectively maintain these things, passing them from one generation to the next like civic heirlooms. And at the very bottom, in the deepest stratum, we find boundary lines. Doug Allen, the Georgia Tech professor whose work inspired this book, described cities as having two orders: *constitutional* and *representational*. The constitutional order consists of the permanent framework: the streets, boundaries, public spaces, and monuments that endure for centuries or millennia. The representational order includes everything else: the buildings, businesses, people, and activities that animate the constitutional framework but change with each generation. The constitutional order is the stage, and the representational order is the play. The actors, costumes, and scenery change with each performance, but the stage remains constant. At the foundation of this constitutional order lie boundary lines, the invisible legal demarcations that separate public from private, mine from yours. While life churns away at the surface, these lines persist at the foundational level for thousands of years. Take Imola, Italy. Two thousand years ago, Roman surveyors divided this territory into large squares, each subdivided into a hundred smaller squares called *heredia* (from the same root as our word "hereditary"). The Romans understood they were creating something meant to be inherited, passed down through generations. And it worked. Through the apex of the Roman Empire and its subsequent collapse, through medieval times when everyone retreated behind city walls, through the Renaissance, the industrial revolution, two world wars, and into our age of smartphones, those same boundary lines still guide Imola's growth today. ![[imola-italy.png]] You can't see boundary lines directly. They're legal abstractions. But over time, they become visible through their physical manifestations: fences spring up along them, buildings align to them, and most importantly, streets follow them. Of all the elements in the constitutional order, streets are one of the most important. By streets, I don't mean just the asphalt or the traffic they carry. I mean the legal right-of-way, the publicly owned land between private properties. The functions found within a right-of-way may change over time, but the legal boundaries of the street can persist for millennia. Streets possess two characteristics that give them their staying power: First, they're collectively owned. Each member of the public has a stake in the streets. It's relatively easy for one person to tear down their own building, but try moving a street and you'll face the resistance of thousands. Every property owner depends on that street for access. Every business depends on it for customers. Every resident has adapted their life to its presence. The sheer inertia of collective ownership locks streets in place. Second, streets are inherited assets that improve over time. A street might begin as a rutted dirt path, but over generations it accumulates investments: gravel, then asphalt, then sidewalks, then street lamps, trees, underground utilities. Each generation inherits what the previous one built and adds their own improvements. Unlike private buildings which often deteriorate between owners, public streets tend to get better with age. When London burned in 1666, the fire destroyed most of the old walled City, some 13,000 houses. Christopher Wren, one of history's greatest architects, saw opportunity in the ashes. He proposed a new street plan with broad avenues radiating from grand squares, importing the latest ideas from Rome. But the old property lines reasserted themselves like a legal ghost. London rebuilt largely along its ancient streets. The same thing happened in San Francisco in 1906. Days before the earthquake and fire destroyed some 28,000 buildings, Daniel Burnham had delivered his *Plan for San Francisco* consisting of new boulevards and civic centers. Here was the perfect chance: across the burned district, hardly a building stood in the way. Yet when the smoke cleared, San Francisco rebuilt along its existing grid. The boundary lines had survived even when nothing else had. ![[san-francisco-fire.png]] This permanence is both urbanism's blessing and its curse. When we get streets right, we create frameworks that can gracefully accommodate centuries of change. Manhattan's 1811 street grid has absorbed everything from horse carriages to skyscrapers, adapting to technologies and densities its creators never imagined, and it still works. But when we get streets wrong, we condemn generations to live with our mistakes. Unnecessary curves that force people to drive, superblocks that kill retail vitality, cul-de-sacs that destroy connectivity: each does its own damage, and the damage compounds. These failings persist with the same stubborn permanence as successes.[^3] This is deep time design. When we draw street lines, we're not just organizing space for current residents; we're creating the framework that will shape lives for centuries, possibly millennia. Those lines will outlive the planner, the client, even the civilization that drew them. They'll persist through technological revolutions we can't imagine and social changes we can't foresee. ![[Urbanism Layers Diagram.png]] Given these stakes, you might assume that modern city planning would focus obsessively on getting streets right. But that's not what happened. Somewhere in the early 20th century, the careful art of laying out streets, once considered the very foundation of city planning, got buried under zoning codes and traffic engineering standards. We started designing cities backward, focusing on land use (what goes where) instead of the permanent framework (the streets and blocks that will outlast any particular use). We prioritized separating things (houses from shops, offices from restaurants) without first ensuring we had a framework that could gracefully accommodate any of these uses as they inevitably shift and change. Frederick Law Olmsted Jr., who led the first national conferences on city planning, put it simply: *"The street plan [is] the foundation of all city planning."*[^2] Yet today, many planners have never learned (or have set aside) these insights. Streets have been reduced to mere traffic sewers, their deeper purpose as the permanent framework of cities largely ignored. This book is about recovering that lost knowledge. It's about understanding why the street plan must come first, before zoning, before architectural guidelines, and before economic development strategies. Because unlike buildings, businesses, or even the people who inhabit them, streets are, for all practical purposes, permanent. We'd better get them right. *** Continue to [[Chapter 2 - What is a Master Street Plan]] → [^1]: Building life expectancies are discussed in Brenda Scheer, "The Anatomy of Sprawl," _Places_ 14, no. 2 (2001). [^2]: Frederick Law Olmsted Jr., introductory address to the Second National Conference on City Planning, Rochester, 1910. The full sentence: "The street plan has always been regarded as the foundation of all city planning." [^3]: The commissioners who laid out Manhattan made one mistake they could not take back: they left out alleys (see [[Chapter 6 - The Four Essential Rules]]). --- Annotations: 0,9493 SHA-256 b606d78bf7faf21db6f3 &Claude: @Paul Knight: ...