Slogans of protest and political or social commentary graffiti on walls are the precursor to modern graffiti and street art, and continue as one aspect of the genre. Street art in the form of text or simple iconic graphics of corporate icons can become well-known yet enigmatic symbols of an area or an era. Some credit the Kilroy Was Here graffiti of the World War II era as one such early example; a simple line-drawing of a long-nosed man peering from behind a ledge. Author Charles Panati indirectly touched upon the general appeal of street art in his description of the "Kilroy" graffiti as "outrageous not for what it said, but where it turned up". Much of what can now be defined as modern street art has well-documented origins dating from New York City's graffiti boom, with its infancy in the 1960s, maturation in the 1970s, and peaking with the spray-painted full-car subway train murals of the 1980s centered in the Bronx.
