Halloween’s origins date back to the ancient Celtic festival of Samhain (pronounced sow-in). The Celts, who lived 2,000 years ago in the area that is now Ireland, the United Kingdom and northern France, celebrated their new year on November 1.

This day marked the end of summer and the harvest and the beginning of the dark, cold winter, a time of year that was often associated with human death. Celts believed that on the night before the new year, the boundary between the worlds of the living and the dead became blurred. On the night of October 31 they celebrated Samhain, when it was believed that the ghosts of the dead returned to earth.

In addition to causing trouble and damaging crops, Celts thought that the presence of the otherworldly spirits made it easier for the Druids, or Celtic priests, to make predictions about the future. For a people entirely dependent on the volatile natural world, these prophecies were an important source of comfort and direction during the long, dark winter.

To commemorate the event, Druids built huge sacred bonfires, where the people gathered to burn crops and animals as sacrifices to the Celtic deities. During the celebration, the Celts wore costumes, typically consisting of animal heads and skins, and attempted to tell each other’s fortunes.

When the celebration was over, they re-lit their hearth fires, which they had extinguished earlier that evening, from the sacred bonfire to help protect them during the coming winter.

By 43 A.D., the Roman Empire had conquered the majority of Celtic territory. In the course of the four hundred years that they ruled the Celtic lands, two festivals of Roman origin were combined with the traditional Celtic celebration of Samhain.

The first was Feralia, a day in late October when the Romans traditionally commemorated the passing of the dead. The second was a day to honor Pomona, the Roman goddess of fruit and trees. The symbol of Pomona is the apple, and the incorporation of this celebration into Samhain probably explains the tradition of “bobbing” for apples that is practiced today on Halloween.

On May 13, 609 A.D., Pope Boniface IV dedicated the Pantheon in Rome in honor of all Christian martyrs, and the Catholic feast of All Martyrs Day was established in the Western church. Pope Gregory III later expanded the festival to include all saints as well as all martyrs, and moved the observance from May 13 to November 1.

By the 9th century the influence of Christianity had spread into Celtic lands, where it gradually blended with and supplanted the older Celtic rites. In 1000 A.D., the church would make November 2 All Souls’ Day, a day to honor the dead. It’s widely believed today that the church was attempting to replace the Celtic festival of the dead with a related church-sanctioned holiday.

All Souls Day was celebrated similarly to Samhain, with big bonfires, parades, and dressing up in costumes as saints, angels and devils. The All Saints Day celebration was also called All-hallows or All-hallowmas (from Middle English Alholowmesse meaning All Saints’ Day) and the night before it, the traditional night of Samhain in the Celtic religion, began to be called All-Hallows Eve and, eventually, Halloween.

Celebration of Halloween was extremely limited in colonial New England because of the rigid Protestant belief systems there. Halloween was much more common in Maryland and the southern colonies.

As the beliefs and customs of different European ethnic groups as well as the American Indians meshed, a distinctly American version of Halloween began to emerge. The first celebrations included “play parties,” public events held to celebrate the harvest, where neighbors would share stories of the dead, tell each other’s fortunes, dance and sing.

Colonial Halloween festivities also featured the telling of ghost stories and mischief-making of all kinds. By the middle of the nineteenth century, annual autumn festivities were common, but Halloween was not yet celebrated everywhere in the country.

In the second half of the nineteenth century, America was flooded with new immigrants. These new immigrants, especially the millions of Irish fleeing the Irish Potato Famine, helped to popularize the celebration of Halloween nationally.

Borrowing from Irish and English traditions, Americans began to dress up in costumes and go house to house asking for food or money, a practice that eventually became today’s “trick-or-treat” tradition. Young women believed that on Halloween they could divine the name or appearance of their future husband by doing tricks with yarn, apple parings or mirrors.

In the late 1800s, there was a move in America to mold Halloween into a holiday more about community and neighborly get-togethers than about ghosts, pranks and witchcraft. At the turn of the century, Halloween parties for both children and adults became the most common way to celebrate the day. Parties focused on games, foods of the season and festive costumes.

Parents were encouraged by newspapers and community leaders to take anything “frightening” or “grotesque” out of Halloween celebrations. Because of these efforts, Halloween lost most of its superstitious and religious overtones by the beginning of the twentieth century.

By the 1920s and 1930s, Halloween had become a secular, but community-centered holiday, with parades and town-wide Halloween parties as the featured entertainment. Despite the best efforts of many schools and communities, vandalism began to plague some celebrations in many communities during this time.

By the 1950s, town leaders had successfully limited vandalism and Halloween had evolved into a holiday directed mainly at the young. Due to the high numbers of young children during the fifties baby boom, parties moved from town civic centers into the classroom or home, where they could be more easily accommodated.

Between 1920 and 1950, the centuries-old practice of trick-or-treating was also revived. Trick-or-treating was a relatively inexpensive way for an entire community to share the Halloween celebration. In theory, families could also prevent tricks being played on them by providing the neighborhood children with small treats.

Thus, a new American tradition was born, and it has continued to grow. Today, Americans spend an estimated $6 billion annually on Halloween, making it the country’s second largest commercial holiday after Christmas.