Billy Joel grew up near New York City and always had an affinity for the city. After he moved to Los Angeles in 1972 to establish his solo career, New York fell on hard times with rampant crime, a huge drug problem, and financial problems that put the city in danger of default.
On October 29, 1975, President Gerald Ford gave a speech where he made it clear that the US government would not bail out New York City to keep it from bankruptcy. The next day, the headline in the Daily News read: "FORD TO CITY: DROP DEAD" (Ford never said these words, and the sensationalist headline hurt him in the next election, which he lost to Jimmy Carter).
Relocated to Los Angeles, Joel found himself around people with little sympathy. "Everybody in LA at the time was like, 'ha, we can't wait to see New York go down the tubes, we hate New York,'" he told Howard Stern in 2014. "And I go, 'I'm going back.' If New York is going down the tubes, I'm going to go back."
Billy did return to New York in 1975, where he wrote this song thinking of the worst-case scenario: financial collapse, murders, looting - an apocalyptic vision that would look like something out of the Mad Max movies. The story Joel came up with was science fiction, but it was based on very real concerns.