Historically, interracial marriage had been illegal in most of the United States, and was still illegal in 17 Southern U.S. States until June of the movie's premiere year.
"Guess Who's Coming to Dinner" is the story of an affluent white girl Joey Drayton (Katharine Houghton) and prominent black doctor John Prentice (Sidney Poitier). After falling in love on vacation, the movie begins as they come to the San Francisco home of Joey's successful and influential parents Matt (Spencer Tracy) and Christina (Katharine Hepburn). Although the two consider themselves to be socially progressive, the prospect of this interracial marriage startles both of them – especially Matt. The situation becomes even more entangled when John tells Matt that he won't marry Joey without Matt's blessing, a factor that becomes exacerbated by the couple's insistence that they get married immediately.