Halloween is celebrated by Western Christians as part of the observance of All Saints Day, which is celebrated annually on November 1. However, Halloween is actually a Christianized pagan festival from Northern Europe that was brought into the United States by Scottish and Irish immigrants.
Many scholars agree that the observance of Halloween was taken from the Celtic harvest festivals. In European traditions, Halloween is also believed to be the time when magic is most powerful and beings from the spirit world gain the ability to make contact with the physical world. This is the reason why Halloween is associated with ghosts, vampires and other supernatural creatures. Halloween started to become commercialized in the early 1900s and the custom of trick-or-treating began in the 1950s.