Halloween originated from the ancient Celtic festival of Samhain, a harvest celebration observed in parts of Britain and Ireland. People lit bonfires and wore costumes to ward off ghosts as winter approached, and over time these practices blended with Christian observances, evolving into the Halloween we know today. The holiday migrated to North America with Irish and Scottish immigrants in the 19th century, where it increasingly featured activities such as trick-or-treating, jack-o’-lantern carving, costume-wearing, and communal celebrations. Modern Halloween is largely secular, though its roots reach back to Samhain and early All Saints’ Day traditions.