Panels from Marvel Graphic Novel: The Pitt one-shot (April 1988); script by John Byrne and Mark Gruenwald; pencils by Sal Buscema; inks by Stan Drake; ink assists by Chris Ivy and Donald Hudson; colors by Janet Jackson; letters by Agustin Mas, Michael Heisler, and Rick Parker
Wikipedia, the Encyclopedia that didn't exist in the New Universe, tells us:
The crater itself is referred to as The Pitt, as is the event that created it. The destruction of Pittsburgh (and the unsolved mystery of its cause) leads to a dramatic rise in international tension and a vast militarization of American society, including the suspension of civil rights. Many cities suffer dramatic drop in population as residents fear becoming victims of another "Pitt." New York and surrounding areas in particular suffer severe economic downturn as, in addition to general depopulation, ash and smoke drifting Eastward from the Pitt have a negative environmental impact.Ladies and gentlemen, I present to you The New Universe: the world outside your window.