Pig Demonstration with Harley and Penelope Domestic Pigs at Children's Zoo on National Pig Day, March 1, 2009 at Brookfield Zoo. First created in 1972 by two sisters, Ellen Stanley of Texas and Mary Lynne Rave of North Carolina, National Pig Day celebrates and appreciates one of the most intelligent of the farmyard animals—the pig. At Brookfield Zoo, guests enjoyed pig-related activities and the Children's Zoo pigs!