Percy Street is one of those irregular side streets found in older American neighborhoods like South Philadelphia. Cramped and dark, it became a favorite haunt of ne'er-do-wells until the installation of the neon-infused "Electric Street" mural. Now it's a destination of locals and tourists, and the increased traffic has tamped down the bad behavior.
Streets Dept has the lowdown:
Until the lights of this electric installation were switched on, Percy street, as legend has it, was a rather convenient spot for criminal behavior. Hidden in the midsts of some of South Philly's most drunkardly bars, a mere three bites away from the Times Square of 24-hour cheesesteaks, the privacy of Percy street offered all those who sought it solace from concerning eyes. This in turn resulted in countless after hour shenanigans, not the least of which included: underaged drinking, prostitution, and short dumping. (I had to Google that too, don't feel bad.)
There's also a cool mirror mosaic acrosss the street that has great opportunities for selfies or artsy urban photo ops. Here's a Google Maps pin, but if you know the area, it's two short blocks south of cheesesteak mecca Geno's.