How about until we've turned them into Boston? Boston and Manhattan are congested, admittedly, but Boston at least (I can't personally speak for Manhattan) is a wonderful place to live. It's a normal, natural, _human_ city, with medium-height buildings and mixed commercial and residential land use (businesses at street level, residences above and sometimes below); it's a far cry from the typical suburban wasteland, half Le Corbousier and half Leave it to Beaver.

Boston is much less dense than Manhattan and much more pleasant to walk in. Some of it is that there are fewer skyscrapers to block the sun. Some of it is the colors -- more red brick and green trees.

I agree strongly. But Boston as well as Manhattan is denser than SF (from what I've heard of SF); in answer to teacup50's question, I'd say "first develop to Boston levels, which are clearly still humane and habitable, then revisit the density issue after that."

Boston's average population density is 13.3k/sq mi.

San Francisco's average population density is 18.5k/sq mi.

SF has been developed beyond Boston levels, and it's still not enough.

Manhattan is actually cheaper than SF now, and they have easy public transit from all different areas (Brooklyn, Queens, Bronx, New Jersey, Yonkers, Staten Island, Long Island) where the lower classes can actually afford to live and commute into the city easily for work. It's much better laid out and planned than SF Bay Area.

Manhattan is only cheaper than SF because SF's market has been driven completely insane by local industry.

Manhattan is still wildly expensive.