Pay a visit to San Francisco's Twin Peaks and you'll gaze upon miles of the city's Victorian row homes, postmodern houses, and low-rise apartment buildings. Way off in the distance, you'll see the skyscrapers, roped off to their little section by the water. Unless you've been paying attention to the Bay Area's housing crisis, your first thought at this sight probably wouldn't be "Where are all the high-rises?" But with home prices steadily climbing in San Francisco since the 1980s, the height of the city has been on the minds of developers and city planners.

Building taller creates more housing and, in theory, an increase in supply should decrease demand and bring down prices. Some San Franciscans haven’t altogether trusted this logic to account for the city’s working class, while others have counted on it to maintain their property values. A highly participatory planning process allows neighborhood groups to contest each new construction project and the city’s leadership wring their hands as they welcome tech jobs into the city but fail to come up with places for their new populace to live. San Francisco’s housing issue is incredibly sticky, with many different interest groups involved, but if the city hopes to maintain any sort of middle class, it will need to promote denser developments.

Earthquakes, by the way, aren’t really a factor. Structural engineers are confident that modern high-rises can withstand even the worst seismic activity. Instead, the city’s height restrictions go back to efforts made in the 1970s and 1980s by a coalition of preservationists, environmentalists, and affordable housing advocates to limit growth in their neighborhoods.

While each group had different aims, they saw how growing pains in other cities affected their respective causes. The environmentalists feared that the expanding downtown would encroach on parks and cut off sunlight and views of the bay, while preservationists hoped to prevent the destruction of San Francisco’s historic architecture. Affordable housing advocates wanted slow-growth policies to prevent the displacement of low-income residents through urban renewal, rising rents, and evictions, and middle-class homeowners were concerned about rising property taxes and traffic congestion

Together, this slow-growth coalition was able to accomplish a lot, including imposing a 40-foot limit on all buildings in residential areas as well as Proposition M, a citizen-sponsored initiative that limited the amount of high-rise developments the city could approve to 475,000 square feet per year. The high-rise cap was the first of its kind in the country and while critics said that it hurt economic growth, Prop M did save San Francisco from overbuilding. By the late 1980s, cities that left construction up to the market faced steep office vacancy rates, while San Francisco hovered at 10-13% vacancy.

No one could have foreseen the tech boom, however, and Prop M did not ensure enough housing for the new jobs invited into the city. The limited supply of office space has also led to rising office rents, and all businesses are more vulnerable as a result. A new architectural trend hoping to address this problem is the “vertical neighborhood,” a mixed-use high-rise (or group of high-rises) with space dedicated to residential and commercial use. San Francisco is trying out the idea on Rincon Hill, a former industrial area. Replacing the old factories and warehouses are tall towers interspaced with mid-rises and townhouses. To avoid exacerbating the problem, a portion of the new units are set aside for affordable housing. The newest apartment tower, Solaire, features eight stories of affordable apartments on the east end of the block.

Elsewhere, the city is creating incentives to entice builders into including more affordable units in their plans. Under the Affordable Housing Bonus Program, developers can build higher and denser than legal limits typically allow if they include more homes for low- and middle-class families. Buildings with 13-20% affordable units get an extra story, while 100% affordable housing developments are allowed to build up to three stories above the existing height limits.

These incentives are encouraging, but some argue that more still needs to be done to prepare for the next wave of newcomers. Plan Bay Area predicts that 800,000 new households will move to the region by 2040, home prices and rents will rise further, and low-income residents will spend 67 percent of their income on housing and transportation. While it’s easy to overestimate growth in the midst of a boom, these forecasts need to be taken seriously. San Francisco has a good thing going, and so has long been an expensive place to live. Part of what makes it great, however, is its diverse community and innovative companies. San Franciscans would be wise to keep these things around.