A passport is obviously required when travelling to countries outside of the United States.
In mom's case, her passport became her primary identification when I was working with notaries and attorneys. When signing legal documents and contracts, such as a Power of Attorney, mom's valid passport was useful since her driver's license was expired. Since mom was blind and could no longer drive her car, having a valid license was no longer important to her.
But having valid identification became important during the last year of her life.
