The Pittsburgh Zoo & Aquarium is a zoo and aquarium in the United States, one of only six major zoo and aquarium hybrids in the United States. First opened in 1898 as the Highland Park Zoo, the zoo evolved from a menagerie to a conservation-focused institution. Pittsburgh saw its zoo grow beginning in the late 1930s when the Works Progress Administration and donations from foundations spearheaded expansions, including then the second largest aquarium in the United States.