The Pennsylvania Farm Show, which began in 1917, is among the largest annual agricultural expositions in the United States. It is held every January in Harrisburg PA, usually over 10 days, during the first and second weeks of the month. Pennsylvania winters don't hinder visitors, because the show's 24-acre complex is almost entirely enclosed. For those interested in farming, or who want to learn more about how foods reach the table, it's highly entertaining.
Better still, it's free. There is no admission charge to the show, although tickets are sold for a limited number of special events.