The main setting for After This is New York City and Long Island, although those physical locales do not have much affect on the story. Readers are vaguely aware of where the characters live, but the novel’s events could take place in any big city or in any suburb.
What plays a bigger role is the book’s general time period, which extends between World War II and the Vietnam War. The wars profoundly affect every character directly or indirectly. The soldiers who come home are unable to readjust to normal life, and the soldiers who do not make it home leave irreparable holes in the families they have left behind. The time period’s moral and social conventions of (particularly those of the 1950s and 1960s) also strongly influence the characters. For example, a woman in her thirties, it is implied, should be married, and a husband should be responsible for bringing home money.