The origins of Halloween can be traced back to the ancient Celts, but trick-or-treating -- the most significant aspect of Halloween -- is a U.S. phenomenon. By the early 1900s, many people associated candy-giving with Christmas and Easter, Samira Kawash write in "The Atlantic." It wasn't until decades later, however, that U.S. candy makers persuade people to buy candy on a large scale to give out to costume-clad strangers at their front doors.

1950s Marks the Spot

Although some people dressed up in costume and hit the streets for Halloween in the 1930s, trick-or-treating was relatively unheard of before the 1950s. It was during the '50s that candy makers recognized the potential of the holiday as a big seller and began advertising inexpensive candy for people to give out as a way to keep from being "egged," "tissue-papered" or otherwise vandalized by unhappy Halloween enthusiasts.