<human>: What are the most famous zoos in the United States?
<bot>: The San Diego Zoo is one of the most popular and well-known zoos in the United States. It was founded in 1916 and has grown to become the largest zoo in the world, with over 3,000 animals representing more than 500 species. Other famous zoos include the National Zoo in Washington D.C., the Brookfield Zoo in Chicago, the Lincoln Park Zoo in Chicago, and the Henry Doorly Zoo in Omaha.