May’s wedding dress represents, rather obviously, the state of her marriage with Archer. It’s customary for brides to wear their wedding dresses a few times in the years immediately after their weddings, and May wears hers to the opera on the night that Archer decides to tell her he’s leaving her. On the way home, just before Archer tries to be honest with May about his feelings for Ellen, she catches her wedding dress in the carriage door, and it tears and gets dirty. Thus, throughout the following scene, in which Archer does not confess his betrayal to May, but instead finds out that Ellen is moving to Europe, May’s torn and soiled wedding dress represents the destruction of their marriage, even though the marriage is still intact according to law and custom.
The timeline below shows where the symbol Wedding Dress appears in The Age of Innocence. The colored dots and icons indicate which themes are associated with that appearance.