In the past few weeks, it has been hard to miss the spider webs, ghosts and tombstones popping up in neighborhoods. If you think Halloween decorations have grown bigger and more elaborate in the past few years, you are probably right.

Nearly half of Americans said this year that they planned to dress up their house for the holiday, according to surveys by the National Retail Federation, a group that advises business.

But traditionally, Halloween was less about decorations than costumes. The tradition started about 2,000 years ago in what is now Ireland with an annual festival of the dead. Revelers would dress up in costumes to scare off evil spirits that roamed the land just before winter arrived.

By about 1000 A.D., the celebration had turned into All Souls’ Day, and poor families would go door to door, asking for food in exchange for prayers for the homeowners’ dead relatives. The two practices merged when costumed children began visiting houses to perform a “trick” in exchange for a “treat” of coins, nuts or fruit.

You can thank Irish immigrants for bringing the idea of trick-or-treating to the United States in the 19th century. It became popular in the 1920s but stopped during World War II, when families had to conserve sugar. Trick-or-treating returned in force during the 1950s.

These days some kids attend parties instead of going door to door, but adults are still prepared: More than 70 percent of Americans said they will be handing out candy Monday night. And they’re hoping kids also enjoy the scary scenery.

So now that you know a bit about why we celebrate Halloween, here are a few more pieces of trivia (thanks to the Retail Federation) for you to chew on along with your Laffy Taffy:

–Americans will spend $8.4 billion on Halloween.

–More than 3 million kids will dress up as a superhero, the most popular costume. Princess and animals took second and third place.

–Sixteen percent of families will dress up a pet. The top three picks: pumpkin, hot dog and bumblebee.

–Seventy-two percent of parents say they will take candy from their children’s stash.

–Seventy-two percent of people say chocolate candy is their favorite.

–One hundred percent of kids should keep an eye on their candy – but also treat Mom and Dad to their chocolaty favorites.