Philadelphia Zoo's Sesquicentennial
America's oldest zoo celebrates its 150th anniversary in 2009. Home to over 1,500 animals spread across 42 acres, the zoo hosts 225,000 school children every year. It was the first zoo to instruct as well as display, and the first to house a research laboratory for the welfare of its residents. The zoo sees its animals as ambassadors of their species, and of wildlife in general.