Masked Halloween MysteryDecked out for Halloween, a masked woman on roller skates—most likely a random addition to her costume—poses in 1910.Masquerade parties in the United States were much more common a hundred years ago, when people dressed up not just for Halloween but also for several other holidays, including Valentine's Day and New Year's Eve, according to Lesley Bannatyne, author of the forthcoming book Halloween Nation: Behind the Scenes of America's Fright Night.Private social clubs often threw Halloween parties for their members, as it was the first major holiday after most people had returned from their summer homes, Bannatyne noted. (Take a quiz: Halloween, harvests, and honoring the dead.)That said, it's "not like Halloween [in the early 1900s] was an East Coast phenomenon or a high-society phenomenon"—people of all classes donned costumes across the country, even in small Western mining towns, she said.(Read about 2010's most popular costumes and other Halloween facts.)The "early 20th century also was the beginning of a real democratic movement, a push toward a popular culture," Bannatyne said, so Halloween was "very egalitarian—everyone celebrated it in their own way."—Christine Dell'Amore

Photograph copyright DaZo Vintage Stock Photos, Images.com, Corbis