From an Ancient Civilization

For many Canadians, the end of October means fall winds down and preparations for the long winter season begin. Furnaces are turned on, winter coats are brought out and freshened up, and people of all ages look forward to a night of mischief, mayhem and good clean fun.
Halloween begins for many on Devil's Night— the night before trick-or-treating where kids throw rotten eggs and paper local houses, generally engaging in tomfoolery for one allowable evening. By dusk on the following day, seemingly endless streams of youngsters trick-or-treat far into the night wearing a large assortment of costumes. How did these traditions begin?
Samhain
Like many of our modern-day celebrations, Halloween evolved from celebrations and age-old practices of ancient people, in thiscase, the Celts. The Celtic people lived in a world very different from ours today, and many of their celebrations were seasonal; they depended on the motions of their agrarian life. Known as the Wheel of the Year, the pagan calendar is divided into eight different festivals (Celtic and Solar) meant to celebrate various different stages within the farming communities, and the cycles of Nature herself. Of the four Celtic festivals, Samhain (pronounced "sow'inn") was the most important.
Samhain, a New Year celebration, represented a time where spirits roamed freely before moving on to their final resting places. For a short period, the boundary between life and death was believed to be blurred. Huge communal bonfires were burned, lanterns were lit to guide the spirits along, animal sacrifices were made, and a great feast was eaten. Druids told fortunes, members of the community celebrated in costumes, and thanks were given for a bountiful harvest.
The Christian Influence
Pagan celebrations evolved as a result of myriad influences. When the Romans ruled over the Celtic lands (modern-day Ireland, Britain, Scotland, Wales and a small part of Northern France), aspects of their own harvest/autumn festivals became interwoven with the already existing local ones. The most overwhelming changes to pagan beliefs and festivals came when the influence of Christianity began to eradicate the old ways, replacing them with church-sanctioned holidays.
By 837, Pope Gregory IV had declared the church-wide observance of All Saint's Day on November 1, perhaps to sanctify the celebrations of Samhain, thus incorporating aspects of the pagan festival into the Christian feast to meant to "glorify God for all God's saints, known and unknown." In medieval England at the time, All Saint's Day was commonly known as All Hallows—"hallow" being the Old English word for "saint." October 31 then came to be known as All Hallows Eve, or Hallowe'en.