National Historic Landmark - Cincinnati Zoo Historic Structures

The second oldest zoo in the United States, it opened to the public in September 1875.

Significant for the antiquity and richness of its collections and for its efforts in the propagation and nurture of rare and endangered species, it was well-known as the home of "Martha" the last passenger pigeon.

The Aviary, where she lived, and the original Monkey House and Herbivore (Elephant) House are the zoo's earliest surviving structures

Courtesy National Park Service National Historical Landmarks