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On some days in downtown San Francisco the yellow and orange hard hats of construction workers bobbing along the sidewalk seem to outnumber the laptop-toting tech workers.

San Francisco is going aggressively vertical, with a building boom of high rises in a city that was once proud of its low-rise, European-style ethos. Today we published an article that looks at the seismic risks of a denser and taller San Francisco — a city straddled by two of the most active faults in North America.

But “skyscraper” was once a dirty word in San Francisco. High rises were demonized in the 1970s by a generation of activists who battled against the “Manhattanization” of the city. The man who spearheaded the anti-skyscraper campaign, Alvin E. Duskin, now lives in a charming wooden house in the rolling hills of northwestern Marin County.

He recently spoke to us about the two ballot initiatives he organized in the 1970s that would have outlawed buildings taller than six stories.