You'll have to pardon our collective "duh": Sunset Boulevard is the name of the movie's setting. The main events unfold in Norma Desmond's "grim sunset castle" located right on that very street. Also, since the film is about the dark side of the movie biz, and Sunset Boulevard is a famous street in Hollywood, it makes a certain degree of Captain Obvious-style sense.

If we want to look a little deeper, though, it seems that the name has a certain poetic quality. California is in the West—where the sun sets, after all—and this is a movie about decline and decay. Norma Desmond, this silent-era star, has entered her own sunset phase, falling from her peak as a world-famous celebrity to a mostly forgotten has-been.

So yeah, this isn't a movie about careers and dreams coming to fruition. Quite the opposite, in fact. Sunset Boulevard depicts Hollywood as a place where dreams go to die—or to be fulfilled for a little while before winding up drowned in the nearest pool. This happens to Norma and to Joe Gillis (since he's a failing writer), but it also happened to Betty before she settled on pursuing a career in writing. (She got a nose job to try to become an actress—but people didn't like her acting.) The movie makes California look like a place that both manufactures dreams and obliterates them—all conjured in that one word from the title, "sunset."