(CNN)"I got to 100 and I guess I forgot to die."
Irving Olson is a 103-year-old amateur photographer from Tucson, Arizona and one of more than 50 American centenarians featured in "If I Live to be 100: The Wisdom of Centenarians," a new book from award-winning photographer Paul Mobley.
The idea for the series came to Mobley while he was photographing farmers for his 2008 book "American Farmer: Portraits from the Heartland." He was surprised to learn that many them were centenarians.
"I found myself wanting to learn all the details of their lives, to find out what inspired them to keep going," he wrote in the book.
Mobley then set himself the challenge of traveling to all 50 states -- mostly by car, accompanied by his wife and dog -- and photographing at least one subject in each. He even captured some supercentenarians (people who've reached or passed their 110th birthdays.)
Some of the more unique subjects were identical twins and couples who had managed to make it to 100 together.
In the book's introduction, writer Allison Milionis describes the impact of the images:
"Note the distinctive lines around the eyes and mouths, the tilt of the head, or the position of the hands -- each portrait is as complex as the 100 years lived. Yet in them we recognize love, loss, hope, and grief, and we're reminded that they are the essential ingredients of a full life."