According to an article by Thom Nickels in the Spirit Community Newspapers, 1/15/14, at p. 2, about Philly's City Hall: In 1921, the Philadelphia Police Department recommended lights on the tower to monitor traffic flows. This experiment pleased some when it was initiated several years later, but may on the road could not see the lights. In 1924, a 30-inch, 350-million candle power spotlight from General Electric was put into the north side of the tower, below the clock. The purpose of the floodlight was to catch thieves who might be running on North or South Broad Street.