A large zoo, occupying 35 acres, was founded in 1868, making it the oldest zoo in North America. It is also the only free zoo in America. This park is home to many types of animals, including big cats (lions, tigers), polar bears, gorillas, reptiles, monkeys, gorillas, and others, numbering 1,100 animals, of about 200 species. The park also includes an oak tree, which dates back to 1830, three years before the founding of the city of Chicago.