Local governments require certain things of new apartments. A minimum square foot size. A window in each bedroom. A way to keep occupants safe when the building catches fire.

And, curiously, a parking space. Since the mid-20th century, U.S. cities have insisted that new homes, offices, restaurants, stores, theaters, and practically anything else you could imagine building be built with new parking spaces.

To be sure, parking is an amenity, like a hot tub or a walk-in closet. But a legal requirement? There were two reasons planners thought this made sense. First, cities were afraid that their lack of parking, and generally poor accommodation of automobile traffic, had put them at a disadvantage compared to the then-booming suburbs. Second, residents were reluctant to permit new development if they thought new neighbors would compete for precious street parking spaces. (David Baker and Brad Leibin recall a San Francisco Planning commissioner denying a permit for a two-unit building with a restaurant downstairs, saying, “I moved from Manhattan to San Francisco so I could park.”) And so virtually every large city in the country made parking spaces as fundamental a component of new buildings as staircases.

That’s starting to change. Hartford, Connecticut eliminated parking minimums last year. Other cities, like Buffalo, New York, New York City, and Cincinnati, have selectively relaxed the requirements in certain areas or for certain types of buildings. This month, Minneapolis approved a plan to get rid of parking minimums. And last week, San Francisco became the largest U.S. city to shed the requirement, the culmination of a series of reforms.

Developers will still be able to build parking spaces, of course. But they will no longer be bound by the city’s ancient formulas to provide them. Which means they can again build the mix of early 20th-century buildings for which San Francisco is famous, most of which were illegal to reproduce under the mid-century code. (Though there were workarounds, like building bicycle parking.) In short, as the transit planner Jarrett Walker put it, San Francisco legalized itself.

Why is this happening now? A few reasons: First, cities realized that residents and business owners had higher priorities than “Can I park here?”—and in fact, some of the country’s least-car-friendly cities have become its most desirable. (See: Francisco, San.) Second, all that required parking functioned, as UCLA parking studies doyen Donald Shoup put it, “like a fertility drug for cars,” as lifestyles, budgets, streetscapes, and architecture were warped around the parking space subsidy. With an eye on stemming greenhouse-gas emissions, cities like San Francisco now want to reduce vehicle dependency. Third, providing parking proved to be a very onerous stipulation for developers, adding tens of thousands of dollars to the cost of every new unit. In a city with a never-ending housing crisis, scrapping the required parking space is an easy way to lower construction costs.

Rider Levett Bucknall, a consulting firm that estimates real estate costs, pegged the 2012 costs of building parking spots in San Francisco at $29,000 above ground and $38,000 below ground. (That figure doesn’t include land costs.) In 2006, the Bay Area think tank SPUR estimated a parking space added $25,000 to $50,000 to the construction cost of each new unit in the city.

As Shoup has written, parking requirements reduce the supply of units in new buildings (because building more units can trigger escalating quantities of parking, dramatically hiking construction costs), increase the price of rentals and condominiums, and diminish the total number of lots that get developed at all (because projects with parking just don’t pencil out). In 2016, two researchers found that parking minimums added $1,700 a year in rent for the average tenant, and the national deadweight loss for carless renters was nearly half a billion dollars. Requires parking also changes the way cities look and feel, making it harder to get around without a car. Consider Houston, which famously has no zoning, but maintains a car-centric, sprawly feel through setbacks and parking requirements.

As pressure mounts for cities to tackle greenhouse-gas emissions and reduce housing prices, expect to see more cities following San Francisco’s lead. Looking to park downtown? Ride a bike.