It started out as an attempt to declutter, but as Mr Jim Perry sifted through boxes that had sat unopened for years, he chanced upon a book that did not belong to his family.

The book was instead property of the St Helena Public Library and was likely taken out on loan by Mr Perry’s wife’s grandfather, Mr John McCormick, nearly 100 years ago.

Mr Perry finally returned the book to the library on May 10, as casually as he had found it, telling librarians that “this is an old book that’s been in our family for five generations”. The 75-year-old then left without leaving his name or contact details.

The book, called A Family History Of The United States, was written by historian Benson Lossing and published in 1892, according to US media.

Mr Perry believes the book was borrowed around the time his wife’s grandfather might have wanted to start teaching his young daughters about American history. Mr Perry’s wife’s family has lived in St Helena, a town roughly 100km north of San Francisco, since the 1840s.

As it turns out, the book might have been part of the library’s original collection, and among the first titles available for readers to borrow for a fee.

“This is the oldest one I’ve ever seen, definitely,” said Ms Chris Kreiden, the library’s director. “I mean we’ve had things [checked out for] two or three years, maybe five, but never anything quite this long.”

Given the century that had passed, the book was “falling apart”, Ms Kreiden said. It was worn and the edges of its pages were fragile and brown.

On the last page was a faded stamp of when the book was due to be returned – Feb 21, 1927. An envelope on the cover said the book could “be kept for two weeks”.

The overdue fee? Five cents per day.

The book also had accession numbers, used to identify the library’s collection at the time of its founding.

Those were the numbers that led to the belief that the book was part of the library’s original collection.

The library is said to have had a reading room but charged 25 cents a month for readers who wanted to take books home.

Ms Kreiden decided the book’s epic return would make a good story.

And it did. The story made it to the local news before going national, and eventually reached Mr Perry, who contacted Ms Kreiden to hear more about the book’s history.

“That was very rewarding,” he said. “I didn’t expect it to be worth much.”

The book has since been placed in a display case near the library’s entrance.

As for the fine, the overdue bill was estimated to be at least US$1,700 (S$2,300). But the library has decided not to charge Mr Perry for it.