Americans has become one of America's favorite holidays. Last year Americans spent more than $3 billion last year on Halloween candy, costumes, pumpkins and decorations. Millions of children (and adults!) look forward to this happy event.

But it hasn't always been so. Once upon a time, Halloween was a night to be feared, when the dead walked the earth.

The history of our modern Halloween begins with an ancient Celtic holiday called Samhain (pronounced sow-en). The Celts lived in present day Ireland and England dating to about the 5th Century BC.

For the Celts, Samhain marked the end of summer. The date is generally given as October 31, but it is unlikely that is the exact date.

For the Celts, as for many ancient peoples, the end of summer was an event viewed with dread. Summer represented a time of warmth and plentiful food; with winter the nights became longer, and food was scarce. And for the superstitious mind, long nights were accompanied by unwelcome spirits.

Much of what has been written about Celtic religion about Celtic religion is the product of the writers' vivid imagination. Despite the legends, it's highly unlikely that the Celts sacrificed virgins in burning wicker cages, and they probably didn't dance naked around Stonehenge.

Most reputable historians agree on one of two stories.

According to one, the Celts believed that Samhain was the night on which the spirits of the dead were permitted to return to Earth to find a body to posess. To avoid this unpleasant fate, the superstitious Celts tried two tricks: First, they would douse all of the hearth fires in their village, to trick the spirits into thinking that no one was home. Then, they would don costumes to fool the spirits and wander about in the dark. The real spirits, thinking that the village already was haunted, would then contine on their journey.

Three of the modern Halloween fixtures are said to come from this legend: Ghosts (spirits of the dead) costumes and dark, empty houses.

To mark the end of the night, the villagers then would relight all of their hearth fires from a sacred bonfire built by their priests, the Druids.

A more gruesome version says that part of the bonfire ceremony involved the ignition of a young, innocent village girl. This, however, is more likely Hollywood than history.

The second version of the Celtic holiday says that they celebrated the end of summer with a huge bonfire. Animals and crops would be burned in the fire to give thanks for the summer, and to ensure their return the next year. Costumes of animals were worn to represent the creatures of the forest that had blessed them that year. At the end of the ceremony, each family would take home an ember to light their own winter hearth fires.

Christianity came to the British Isles somewhere around the second century AD. One of the tactics of early missionaries was to make Christianity more palatable by incorporating local customs into Christian practice. For example, early missionaries were willing to abandon the stricture that converts first become Jews when they ran across cultural barriers, and it is thought that the date of Christmas was selected to coincide with a Germanic winter festival.

As the story goes, the Celts were unwilling to give up their summer festival, so the missionaries simply incorporated it.

In the 700s, Pope Boniface IV set November 1 as All Hallows -- or All Saints -- Day. The previous night was thus known as All Hallows Eve. November 2 became All Souls Day, to honor the souls of the dead. The three days together were called Hallow Mass.

And All Hallows Eve became Halloween.

It is widely believed that Boniface IV did this to co-opt the pagan Celtic holdouts into Christianity.

Halloween arrived in North America with the early colonists. However, because of the Puritan influence in New England, it was mostly confined to the Scots-Irish of the Southern Colonies.

Colonial Halloweens were celebrated as Harvest Festivals, with lots of eating and drinking, music, dancing, ghost stories and fortune telling. (All of these were things that were disapproved of in Puritan New England. Some more of our modern Halloween symbols were introduced at this time, as traditions were blended with Native American harvest festivals. Corn stalks and pumpkins - unknown in Europe before the discovery of North America - became part of Halloween imagery.

But Halloween really arrived in America with the massive Irish immigration of the 1840s. The Irish brought their Celtic Halloween traditions with them and wove them into the fabric of American society.