Elsa wore her crown at her coronation party.
Elsa's crown is an item bestowed upon her on the day of her coronation.
History
The crown was given to Elsa as part of the rite of becoming queen; Elsa bowed her head for the bishop to place it on her head where it was held in position by her hair.
After fleeing to the North Mountain and completing her ice palace, Elsa removed the crown and threw it aside. Marshmallow later found the crown in the abandoned palace and put it on his head, lightening his mood.