Observed annually on January 19, this food holiday recognizes a satisfying snack that's often served buttered, salted, kettled or drizzled with caramel. In the United States, more than half of the nation's popcorn is grown in Nebraska, Indiana, Illinois and Ohio. Unlike other kinds of maize or corn, popcorn (Zea mays everta Sturt.) has a thicker hull, allowing pressure from being heated to build up until the gelatinous starch inside bursts out, creating the familiar popcorn shape.