Halloween is a holiday that has its roots in the ancient Celtic festival of Samhain, which marked the transition from the warm, fruitful summer months to the cold and dark winter, a period that was most often associated with death. The Celts believed that on the night before the new year, October 31, the boundary between the living world and the world of the dead became thin, and ghosts could return to walk the earth. They celebrated this night as Samhain, which is considered the earliest known root of our secular Halloween traditions.
The name "Halloween" comes from "All Hallows Eve," which is the evening before the Christian holy days of All Hallows Day (All Saints Day) on November 1 and All Souls Day on November 2. Since the time of the early Church, major feasts in Christianity had vigils that began the night before, as did the feast of All Hallows.
Over time, Halloween has evolved to include many traditions, including carving pumpkins, trick-or-treating, and wearing costumes. Carving pumpkins into jack-o-lanterns is a tradition that originated in Ireland, where people would carve turnips or potatoes to ward off evil spirits. Trick-or-treating has its roots in the ancient Celtic practice of leaving food out to appease the spirits traveling the Earth at night. Over time, people began to dress as these unearthly beings in exchange for similar offerings of food and drink. Wearing costumes and playing pranks were also part of the pre-Halloween tradition known as “Devil’s Night,” which was celebrated during Samhain and eventually All Souls Day.
Halloween has been celebrated in the United States since at least the late 1800s, but the holiday really took off in the 1900s when retailers began mass producing cards, decorations, and Halloween costumes. Today, Halloween is a major holiday in the United States, with Americans spending upwards of $10 billion annually on everything from vintage decorations to pet costumes.