The History of Halloween. The origins of Halloween are believed to date back to the ancient Celtic celebration of Samhain. . Samhain marked the transition from the growing season into winter and was widely celebrated with animal costumes, bonfires and superstitious tales. . After the Romans conquered the Celts in 43 AD, Samhain evolved into the Nov. 1 religious holiday of All Hallows. Because of this, Oct. 31 was marked as All Hallow’s Eve, which is also known as Halloween. From there, Puritan immigrants arrived in America and brought the various traditions of the holiday with them. . All Hallow’s Eve became a time to host “play parties” in celebration of the harvest, many of which included costumes and scary stories. In the 1800s, Irish immigrants arrived in America and introduced the tradition of tricking people on the holiday. . The concept of treats was reinforced later on in the 1930s, in order to control the “tricks” and create a more family-oriented form of celebration. . Candy companies began to fully capitalize on Halloween in the 1950s, inventing the candy we know and love even to this day.