“The origin of what would become Gold Star Mother’s and Family’s Day started with a simple accessory: a black armband with a gilt star.
During World War I, family members would wear these armbands to represent a loved one who had died in the war. The stars would later find their way to being displayed on banners that were hung in windows or front doors. Banners with blue stars were hung to represent immediate family members who were serving. Some would have one star; others would have two or three. The stars symbolized the people who were supposed to be home but were missing from the dinner table. If a family member died during their service, the blue star would be replaced with a gold one.”
Source: Arlington National Cemetery
Military One Source: Honoring Gold Star Families