#1.) Trick-or-treating. It comes from an old tradition where poor children in England and Ireland would go door-to-door praying for the dead on All Saints' Day.

After World War Two, children in the U.S. started doing the door-to-door walk, and people started giving them candy...which led to trick-or-treating.

#2.) Jack-o-lanterns. This comes from an Irish legend about a farmer named Jack who would play tricks on the devil AND God. That got him banned from heaven and hell, so he roamed the world as a flame inside carved vegetables.

Jack-o-lanterns became part of Irish superstition too. People would carve turnips and put them outside their houses to scare away evil spirits. Americans used pumpkins instead because there were more of them and they were easier to carve.

#3.) Haunted houses. These don't come from any tradition except the tradition of people finding a way to MAKE MONEY off holidays. In the 1950s, Junior Chamber International clubs realized they could make money off haunted houses that played off the Halloween spirit, so they did...and everyone else followed their lead.