SPENCER MICHELS:

But now a new wave of tech enterprises are moving into the city and nearby Silicon Valley, bringing with them well-paid workers who can afford to live in newer and more upscale digs and patronize pricey bars and restaurants.

Twitter, with 2,000 employees, recently opened its new headquarters just across the street from the Tenderloin. And that's brought in a few new businesses and put pressure on the city to clean up the area.

I have spent most of my life in and around San Francisco, and I have seen lots of changes, but, somehow, the Tenderloin seems to have avoided that change. It's still not a pleasant place, but it's home for the poor. Many other cities have had places like the Tenderloin, but they have redeveloped them. Somehow, the Tenderloin has resisted that.

One reason San Francisco has not redeveloped the Tenderloin is the city's experience in the largely African-American neighborhood called the Fillmore or Western Addition. In the 1960s, the city declared the area blighted and essentially bulldozed it into oblivion, forcing thousands of blacks to move out of the city. Critics called it black removal.

San Francisco magazine editor Gary Kamiya says that it was a huge mistake.

GARY KAMIYA, San Francisco magazine: The destruction of the Western Addition in the name of urban renewal, probably the greatest sin in the history of San Francisco.