For the past decade and a half, the boxy, squat office building at 215 Fremont St. in San Francisco has helped fuel the city’s financial-services engine, packed with employees of brokerage giant Charles Schwab.

But the building is doing what everything in San Francisco seems to be doing—it is getting gobbled up by the tech sector. Wearable fitness tracker Fitbit Inc. is gradually moving into all of Charles Schwab’s 310,000 square feet, while Schwab is shedding 1,000 jobs in the area in favor of lower-cost locations like Texas.

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