The long-raging debate around facial recognition software, with all the privacy worries it brings with it, has taken on new urgency as the technology has improved and spread by leaps and bounds.

On Tuesday, San Francisco became the first major American city to block police and other law enforcement agencies from using the software.

Here is a look back at some of the many controversies over facial recognition and its use.

The 2001 Super Bowl

In January 2001, the city of Tampa, Fla., used a facial recognition surveillance system as it hosted Super Bowl XXXV.

It was an early real-world example of how the technology could be used and prompted a backlash from privacy advocates including the American Civil Liberties Union.