15 Ideas That Have Helped Shape American Cities

Cities are living things, forever changing and adapting. Over decades and centuries, people have adapted their towns to look and function in certain ways, to ease traffic, maintain a certain visual identity, or improve business. Psychology, local climate, politics, and pure whim all dictate how cities develop over time. Here are 15 reasons the urban world looks and feels the way it does today:

1. As long as there have been cities, there has been an urban grid

Some of the world’s oldest cities were built along grid plans still in use today. Ancient China, Mesopotamia, and Greece [PDF] all had arranged city streets with some version of the north-south and east-west orientations (intersecting at right angles in a chessboard pattern) found in modern metropolises like Chicago. While plenty of ancient cities boasted the twisting, curving alleys of tourists’ nightmares, Hippodamus of Miletus, the “father of city planning,” argued for a more logical organization for cities in the 5th century BCE, calling for geometric streets with public space, markets, government buildings, and houses of worship all centrally located.

2. The ideal length for a city block is about 200 feet

Why do some neighborhoods feel like they take longer to walk around in than others? It’s all about perception. Short blocks make a more comfortable walk, because the scenery changes more often. The ideal city block offers a new route choice about once every minute, according to the Bay Area urban planning nonprofit SPUR [PDF]. This equates to about once every 200-300 feet—the length of a city block in pedestrian-friendly cities like Portland, Oregon.

3. Truly safe speed limits are slower than you'd think

In 2014, Paris set the default speed limit for its streets at less than 20 mph, following a trend embraced by numerous European municipalities. In busy cities, lower speed limits can actually improve congestion, as they help maintain the flow of traffic [PDF]. And lower speed limits dramatically reduce the potential for deadly accidents between cars and pedestrians. In a study by the U.S. National Highway Traffic Safety Administration, only 1.2 percent of accidents between people and cars going less than 20 mph were fatal, compared to over 22 percent of pedestrian accidents involving cars going 50 mph.

4. Entire towns have banned clotheslines, leaving backyards laundry-free

The old-fashioned method of hanging your laundry out to dry in the sun hasn’t just gone out of fashion as electric dryers gained steam. Some communities have eliminated the sight of laundry hanging around town through more direct means. In Levittown, Pennsylvania, for instance, one of the earliest models of the post-war American suburb, they were banned because “old fashioned clothes lines strung across the lawn look messy,” according to the town’s developer, William Levitt. In 2010, the BBC estimated that 60 million Americans lived in "about 300,000 communities governed by home-owning associations," many of which ban clotheslines as an eyesore—so many that multiple states have passed laws saying you can’t be prohibited from hanging your clothes in the sun. 

5. Highways aren’t lined with trees because too many people hit them

The U.S. Department of Transportation reports that trees are the most commonly struck objects in serious roadside crashes. California’s transportation administration, for instance, mandates that all trees be set back at least 30 feet from the road [PDF]. However, whether or not trees actually cause crashes is more controversial. Some urban designers argue that clearing highways of trees makes people drive faster in the first place [PDF], but that line of thinking has yet to become popular enough to re-landscape our freeways.

6. That big parking lot is required by the city

America’s love affair with parking (and lack of widespread mass transit) means that wherever people go, they need to find parking—even at bars, where arguably no one should be driving. Most cities mandate a certain number of off-street parking spaces be built for each new development based on estimates of peak demand. For instance, Cincinnati requires one parking space for every 1,200 square feet of office space. In Austin, a longtime neighborhood restaurant nearly shut down in 2013 because it didn’t provide 50 parking spaces for employees and customers, the city minimum.

7. Diagonal crosswalks keep drivers from turning on top of pedestrians and each other

Drivers tend to dislike them because they result in longer red lights, but diagonal crosswalks—where all vehicles stop at once to allow for unfettered walking access across the intersections—have proven to reduce pedestrian accidents, especially in intersections with a lot of pedestrian traffic. Perhaps the most famous of these crosswalks is Tokyo’s Shibuya crossing, one of the world’s busiest intersections. The diagonal crosswalk (also known as scrambles or “Barnes dances” after a traffic engineer who popularized them in Denver) is making a comeback in the U.S., too, in cities like Los Angeles, Chicago, and San Francisco.

8. Zoning laws arose to try to distance low-brow manufacturing from upscale shopping

In 1916, New York City passed the first comprehensive zoning ordinance in the U.S. [PDF]. Besides regulating tall buildings, it divided the city into residential, business, and unrestricted districts. In business districts, distasteful trades like manufacturing, auto repair, and metalwork were prohibited. A major player behind the law was the Fifth Avenue Association, which was formed in 1907 to stop factory encroachment on the fashionable boulevard. The high-end retailers of Fifth Avenue did not want lowly garment workers shooing away ladies from their shopping [PDF].

9. Does your neighborhood suddenly have a lot of rock gardens? The city paid for that

In drought-stricken Southern California, major cities have begun offering incentives for residents to ditch their thirsty grass lawns. Los Angeles gives property owners rebates for every square foot of lawn they rip up and replace with a drought-friendly option like succulents, getting rid of 1.5 million square feet of grass between 2009 and 2013. In 2014, they upped the kickback for switching to climate-appropriate plants to $3.75 per square foot for up to 1500 square feet, and 2 dollars per square foot after. Other cities, including Pasadena, Long Beach, and Anaheim participate in similar schemes.

10. That new pedestrian plaza owes its design to a snowstorm

After a heavy snow, plows pile snowbanks up around the edges of streets, narrowing the lanes cars can use. For urban designers, these snow tracks illustrate the amount of space cars actually use in an intersection, versus what’s essentially open space. Named after a term for curb extensions—"neckdowns"—these so-called sneckdowns (portmanteau of snow and neckdown) are occasionally used to redesign streets long after the snow has melted to calm traffic and make more room for pedestrians. In Philadelphia, for instance, images of snow-covered streets resulted in approval for more crosswalks and new pedestrian islands at one large intersection.

11. Danger levels determine how many sides a traffic sign has

In the early days of traffic safety, traffic engineers decided sign shapes should indicate the level of danger present in a particular situation. More sides meant more danger. As a result, railroad crossings became round (infinite sides) and stop signs became octagonal, showing drivers that these intersections were treacherous. By contrast, diamond signs alerted drivers that they merely needed to be cautious, and rectangular signs provided non-essential information like directions. The theory was, in an era before reflective coatings and widespread illumination, drivers could respond to a sign’s shape even if they couldn’t read it in the dark.

12. Washington, D.C. buildings can only be as tall as their street is wide

The capital’s buildings are regulated by the Height of Buildings Act of 1910, which maintains that no tower shall rise more than 20 feet taller than the width of the street it faces, and zoning in some neighborhoods prohibits even reaching that height. On certain streets, the 1910 law allows the “extreme height” of 160 feet tall. In recent years, as D.C.’s population and real estate prices have soared, this cap on skyscrapers has become controversial as one of the main drivers of the city’s extremely high rents.

13. New York City marketed Broadway as a theater district to keep it from getting too raunchy

In 1967, New York City passed an ordinance allowing a 20 percent bonus in buildable floor area in new developments if a new theater was also incorporated into the plan, hoping to encourage the growth of more wholesome entertainment in contrast to Times Square’s rising wave of porn shops and prostitution. In the late 1980s, eager to attract new builders while still retaining the vibrancy of a theater district, city officials mandated that all new developments near Broadway allocate a certain percentage of floor space to “entertainment-related uses,” including rehearsal studios, theaters, and costume shops [PDF].

14. Hollywood has palm trees because they made for neater sidewalks

Before the 1930s, the iconic Southern California tree wasn’t a palm, it was a pepper tree. Environmental historian Jared Farmer tells LA radio station KCET this story of L.A.’s transformation into a palmy paradise:

In the age of streetside parking, sidewalks, sewers, and utility poles, these leafy, rooty growers acquired bad reputations. In contrast, palms held out the promise of symbiotic infrastructure: they could provide beautification without dropping fruit, buckling concrete, or breaking pipes and wires.

The Mexican fan palm, the tall, skinny trees that have become an iconic symbol of Hollywood, were chosen because they were cheap and resilient. Hollywood became the dominant force in entertainment around the same time when L.A.’s Depression-era trees matured, cementing the region’s association with the palm with savvy marketing.

15. Colored bike lanes are green to keep people from thinking they're disability parking

In 2011, the Federal Highway Administration gave its interim approval for cities to use green colored pavement to mark bicycle lanes. While there’s no international standard for bike lane colors (London uses blue, the Netherlands uses red), the U.S. decided to go with green, as in, wow, biking sure is good for the environment!

A report [PDF] from the Chicago Department of Transportation sums the rationale up this way:

While CDOT’s findings show that blue is the most tested and widely associated color for colored bike lanes, due to its current association with parking spaces for persons with disabilities, CDOT feels it is unsuitable for colored bike lane pavement markings. Green, on the other hand, is not assigned a meaning for pavement markings in this country.

According to the FHWA’s approval notice, red pavement for bicycling infrastructure is still being tested. Too bad for Portland, Oregon, which pioneered colored bike lanes in the U.S. in the late ‘90s but went with the color blue [PDF].