The passenger pigeon was endemic to North America. Its common name is derived from the French word passager, meaning “passing by”, due to the migratory habits of the species.

In 1902, the Cincinnati Zoo received a female passenger pigeon; this was the individual later known as Martha, which would become the last living member of the species. In 1909, Martha and her two male companions at the Cincinnati Zoo became the only known surviving passenger pigeons. One of these males died around April that year, followed by George, the remaining male, on July 10, 1910.

Martha died of old age on September 1, 1914, and was found lifeless on the floor of her cage. It was claimed that she died at 1 p.m., but other sources suggest she died some hours later.