Last passenger pigeon, Martha, died 100 years back in United States. The species was driven to extinction about a hundred years ago due to aggressive hunting and habitat loss. The birds were most abundant in North America until late 1800s.

Allan W. Eckert's book, The Silent Sky, follows the life of last passenger pigeon. The book was published in 1965.

Author Joel Greenberg has said about the bird in his book named 'A Feathered River Across the Sky: The Passenger Pigeon's Flight to Extinction'. Author said, "More people were probably introduced to the story of the passenger pigeon through 'The Silent Sky' than any other single source".

Greenberg's book has shown complete history and extinction of passenger pigeon. In his book, he stated some of the unbelievable statistics about the remarkable bird.

According to the book, there were several flocks of passenger pigeons over every major city of United States and Canada.

American ornithologist, painter and naturalist John James Audubon had recorded a pigeon flight along the Ohio River that had hid the sun for about three days. Audubon had also shown the beauty of the bird through his painting.
In his book, Greenberg said that in 1860, more than one billion passenger pigeons had exceeded a flight near Toronto. Forty years after that incident, the species have gone extinct. The last passenger pigeon, Martha, died in the Cincinnati Zoo.

In Cheryl Kimball's Nature Talks, Cheryl Kimball said she had visited Cincinnati Zoo for the first time to celebrate 'Thanksgiving'. According to her, the last bird was no longer there. There was a memorial near Martha's cage.

On September 1, Cincinnati Zoo had planned to remember the last passenger pigeon by honoring the bird by renovating its memorial. Apart from that, the zoo hosted a series of lectures and event for Martha.