Some say, Halloween, the contraction for All Hallows' Evening, began in the deep, dark past with the Celtic festival of Samhain. It was a time to celebrate the harvest taken in, stocking up all the goodies for a long, hard winter. Bonfires were a feature of the festivities. Rumor has it those fires drew lots of bugs, calling in lots of bats, hence the bat symbol ... no, not the one on top of the Gotham City police station. However, on a darker note, October 31 was the night when the boundaries between this world and the next thinned and the dead walked the earth. Not peaceful, happy dead, but dead intent on crop damage and disease. However, that name, All Hallows' Eve, is considered a Christian remake of that festival.
But, where does the costuming and the candy crawl come from? For that we go to the Middle Ages practice of Christmas wassailing. Known as souling, the poor would go knocking on the doors of others on November 1, a.k.a. Hallowmas, where they were given food in exchange for prayers for the dead on All Souls Day the next day. This practice stems from Britain and Ireland.
But the heavy costuming does not show up until after 1900 and appears to be of American manufacture. In the 1930s and 1940s, trick or treating caught on in America, sweeping the nation from West to East, its sugary advance slowed by sugar rationing in World War II.
However, candy would be a late arrival on the scene as the booty of choice for trick or treaters. While candy corn originates in the 1880s, the seemingly eternal tradition of candy for Halloween actually took off in the 1950s in America. From an article in The Atlantic, I discovered that the average Halloween Jack-O-Lantern bucket will hold roughly 250 treats, weighing in at 3 pounds of sugar and 9,000 calories. Back away from the bucket parents!
And what of our friend jack, the Jack-O-Lantern. His cheery face was first popularized in Ireland, where turnips, mangelwurzel, or beets were said to be used (any port in a storm, I guess). It is said to have originated with the Christian practice of soul lights, representing the souls of the dead. By Celtic custom, those glowing visages were designed to ward off the restless spirits of the dead seeking to spread disease and damage crops! Now we've come full circle. Happy Halloween.
For more Halloween fun, see: http://jsbrookspresents.blogspot.com/2011/10/more-radio-chills-for-late-halloween.html, http://jsbrookspresents.blogspot.com/2009/05/alien-abductions-and-slavering-monsters.html, http://jsbrookspresents.blogspot.com/2009/04/what-about-boogeyman.html, (in honor of the 75th anniversary of the War of the Worlds radio broadcast) http://jsbrookspresents.blogspot.com/2010/12/nasa-funded-research-discovers-life.html, and http://jsbrookspresents.blogspot.com/2009/05/put-story-back-in-ghost-stories-part-2.html
For more history, see: halloweenhistory.org, http://www.theatlantic.com/health/archive/2010/10/how-candy-and-halloween-became-best-friends/64895/, and wikipedia for quick and colorful histories with lots more to tell. We've only scratched the surface. Happy Halloween.